emacs/lisp/progmodes/python.el

;;; python.el --- silly walks for Python  -*- coding: iso-8859-1 -*-

;; Copyright (C) 2003-2012  Free Software Foundation, Inc.

;; Author: Dave Love <fx@gnu.org>
;; Maintainer: FSF
;; Created: Nov 2003
;; Keywords: languages

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Major mode for editing Python, with support for inferior processes.

;; There is another Python mode, python-mode.el:
;; http://launchpad.net/python-mode
;; used by XEmacs, and originally maintained with Python.
;; That isn't covered by an FSF copyright assignment (?), unlike this
;; code, and seems not to be well-maintained for Emacs (though I've
;; submitted fixes).  This mode is rather simpler and is better in
;; other ways.  In particular, using the syntax functions with text
;; properties maintained by font-lock makes it more correct with
;; arbitrary string and comment contents.

;; This doesn't implement all the facilities of python-mode.el.  Some
;; just need doing, e.g. catching exceptions in the inferior Python
;; buffer (but see M-x pdb for debugging).  [Actually, the use of
;; `compilation-shell-minor-mode' now is probably enough for that.]
;; Others don't seem appropriate.  For instance,
;; `forward-into-nomenclature' should be done separately, since it's
;; not specific to Python, and I've installed a minor mode to do the
;; job properly in Emacs 23.  [CC mode 5.31 contains an incompatible
;; feature, `subword-mode' which is intended to have a similar
;; effect, but actually only affects word-oriented keybindings.]

;; Other things seem more natural or canonical here, e.g. the
;; {beginning,end}-of-defun implementation dealing with nested
;; definitions, and the inferior mode following `cmuscheme'.  (The
;; inferior mode can find the source of errors from
;; `python-send-region' & al via `compilation-shell-minor-mode'.)
;; There is (limited) symbol completion using lookup in Python and
;; Eldoc support also using the inferior process.  Successive TABs
;; cycle between possible indentations for the line.

;; Even where it has similar facilities, this mode is incompatible
;; with python-mode.el in some respects.  For instance, various key
;; bindings are changed to obey Emacs conventions.

;; TODO: See various Fixmes below.

;; Fixme: This doesn't support (the nascent) Python 3 .

;;; Code:

(require 'comint)
(require 'ansi-color)

(eval-when-compile
  (require 'compile)
  (require 'hippie-exp))

(autoload 'comint-mode "comint")

(defgroup python nil
  "Silly walks in the Python language."
  :group 'languages
  :version "22.1"
  :link '(emacs-commentary-link "python"))

;;;###autoload
(add-to-list 'interpreter-mode-alist (cons (purecopy "jython") 'jython-mode))
;;;###autoload
(add-to-list 'interpreter-mode-alist (cons (purecopy "python") 'python-mode))
;;;###autoload
(add-to-list 'auto-mode-alist (cons (purecopy "\\.py\\'")  'python-mode))

;;;; Font lock

(defvar python-font-lock-keywords
  `(,(rx symbol-start
	 ;; From v 2.7 reference, § keywords.
	 ;; def and class dealt with separately below
	 (or "and" "as" "assert" "break" "continue" "del" "elif" "else"
	     "except" "exec" "finally" "for" "from" "global" "if"
	     "import" "in" "is" "lambda" "not" "or" "pass" "print"
	     "raise" "return" "try" "while" "with" "yield"
             ;; Not real keywords, but close enough to be fontified as such
             "self" "True" "False"
             ;; Python 3
             "nonlocal")
	 symbol-end)
    (,(rx symbol-start "None" symbol-end)	; see § Keywords in 2.7 manual
     . font-lock-constant-face)
    ;; Definitions
    (,(rx symbol-start (group "class") (1+ space) (group (1+ (or word ?_))))
     (1 font-lock-keyword-face) (2 font-lock-type-face))
    (,(rx symbol-start (group "def") (1+ space) (group (1+ (or word ?_))))
     (1 font-lock-keyword-face) (2 font-lock-function-name-face))
    ;; Top-level assignments are worth highlighting.
    (,(rx line-start (group (1+ (or word ?_))) (0+ space)
	  (opt (or "+" "-" "*" "**" "/" "//" "&" "%" "|" "^" "<<" ">>")) "=")
     (1 font-lock-variable-name-face))
    ;; Decorators.
    (,(rx line-start (* (any " \t")) (group "@" (1+ (or word ?_))
					    (0+ "." (1+ (or word ?_)))))
     (1 font-lock-type-face))
    ;; Built-ins.  (The next three blocks are from
    ;; `__builtin__.__dict__.keys()' in Python 2.7)  These patterns
    ;; are debatable, but they at least help to spot possible
    ;; shadowing of builtins.
    (,(rx symbol-start (or
	  ;; exceptions
	  "ArithmeticError" "AssertionError" "AttributeError"
	  "BaseException" "DeprecationWarning" "EOFError"
	  "EnvironmentError" "Exception" "FloatingPointError"
	  "FutureWarning" "GeneratorExit" "IOError" "ImportError"
	  "ImportWarning" "IndentationError" "IndexError" "KeyError"
	  "KeyboardInterrupt" "LookupError" "MemoryError" "NameError"
	  "NotImplemented" "NotImplementedError" "OSError"
	  "OverflowError" "PendingDeprecationWarning" "ReferenceError"
	  "RuntimeError" "RuntimeWarning" "StandardError"
	  "StopIteration" "SyntaxError" "SyntaxWarning" "SystemError"
	  "SystemExit" "TabError" "TypeError" "UnboundLocalError"
	  "UnicodeDecodeError" "UnicodeEncodeError" "UnicodeError"
	  "UnicodeTranslateError" "UnicodeWarning" "UserWarning"
	  "ValueError" "Warning" "ZeroDivisionError"
	  ;; Python 2.7
	  "BufferError" "BytesWarning" "WindowsError") symbol-end)
     . font-lock-type-face)
    (,(rx (or line-start (not (any ". \t"))) (* (any " \t")) symbol-start
	  (group (or
	  ;; callable built-ins, fontified when not appearing as
	  ;; object attributes
	  "abs" "all" "any" "apply" "basestring" "bool" "buffer" "callable"
	  "chr" "classmethod" "cmp" "coerce" "compile" "complex"
	  "copyright" "credits" "delattr" "dict" "dir" "divmod"
	  "enumerate" "eval" "execfile" "exit" "file" "filter" "float"
	  "frozenset" "getattr" "globals" "hasattr" "hash" "help"
	  "hex" "id" "input" "int" "intern" "isinstance" "issubclass"
	  "iter" "len" "license" "list" "locals" "long" "map" "max"
	  "min" "object" "oct" "open" "ord" "pow" "property" "quit"
	  "range" "raw_input" "reduce" "reload" "repr" "reversed"
	  "round" "set" "setattr" "slice" "sorted" "staticmethod"
	  "str" "sum" "super" "tuple" "type" "unichr" "unicode" "vars"
	  "xrange" "zip"
	  ;; Python 2.7.
	  "bin" "bytearray" "bytes" "format" "memoryview" "next" "print"
	  )) symbol-end)
     (1 font-lock-builtin-face))
    (,(rx symbol-start (or
	  ;; other built-ins
	  "True" "False" "None" "Ellipsis"
	  "_" "__debug__" "__doc__" "__import__" "__name__" "__package__")
          symbol-end)
     . font-lock-builtin-face)))

(defconst python-syntax-propertize-function
  ;; Make outer chars of matching triple-quote sequences into generic
  ;; string delimiters.  Fixme: Is there a better way?
  ;; First avoid a sequence preceded by an odd number of backslashes.
  (syntax-propertize-rules
   (;; ¡Backrefs don't work in syntax-propertize-rules!
    (concat "\\(?:\\([RUru]\\)[Rr]?\\|^\\|[^\\]\\(?:\\\\.\\)*\\)" ;Prefix.
              "\\(?:\\('\\)'\\('\\)\\|\\(?2:\"\\)\"\\(?3:\"\\)\\)")
    (3 (ignore (python-quote-syntax))))
   ;; This doesn't really help.
   ;;((rx (and ?\\ (group ?\n))) (1 " "))
   ))

(defun python-quote-syntax ()
  "Put `syntax-table' property correctly on triple quote.
Used for syntactic keywords.  N is the match number (1, 2 or 3)."
  ;; Given a triple quote, we have to check the context to know
  ;; whether this is an opening or closing triple or whether it's
  ;; quoted anyhow, and should be ignored.  (For that we need to do
  ;; the same job as `syntax-ppss' to be correct and it seems to be OK
  ;; to use it here despite initial worries.)  We also have to sort
  ;; out a possible prefix -- well, we don't _have_ to, but I think it
  ;; should be treated as part of the string.

  ;; Test cases:
  ;;  ur"""ar""" x='"' # """
  ;; x = ''' """ ' a
  ;; '''
  ;; x '"""' x """ \"""" x
  (save-excursion
    (goto-char (match-beginning 0))
    (let ((syntax (save-match-data (syntax-ppss))))
      (cond
       ((eq t (nth 3 syntax))           ; after unclosed fence
        ;; Consider property for the last char if in a fenced string.
        (goto-char (nth 8 syntax))	; fence position
        (skip-chars-forward "uUrR")	; skip any prefix
        ;; Is it a matching sequence?
        (if (eq (char-after) (char-after (match-beginning 2)))
            (put-text-property (match-beginning 3) (match-end 3)
                               'syntax-table (string-to-syntax "|"))))
       ((match-end 1)
        ;; Consider property for initial char, accounting for prefixes.
        (put-text-property (match-beginning 1) (match-end 1)
                           'syntax-table (string-to-syntax "|")))
       (t
        ;; Consider property for initial char, accounting for prefixes.
        (put-text-property (match-beginning 2) (match-end 2)
                           'syntax-table (string-to-syntax "|"))))
      )))

;; This isn't currently in `font-lock-defaults' as probably not worth
;; it -- we basically only mess with a few normally-symbol characters.

;; (defun python-font-lock-syntactic-face-function (state)
;;   "`font-lock-syntactic-face-function' for Python mode.
;; Returns the string or comment face as usual, with side effect of putting
;; a `syntax-table' property on the inside of the string or comment which is
;; the standard syntax table."
;;   (if (nth 3 state)
;;       (save-excursion
;; 	(goto-char (nth 8 state))
;; 	(condition-case nil
;; 	    (forward-sexp)
;; 	  (error nil))
;; 	(put-text-property (1+ (nth 8 state)) (1- (point))
;; 			   'syntax-table (standard-syntax-table))
;; 	'font-lock-string-face)
;;     (put-text-property (1+ (nth 8 state)) (line-end-position)
;; 			   'syntax-table (standard-syntax-table))
;;     'font-lock-comment-face))

;;;; Keymap and syntax

(defvar python-mode-map
  (let ((map (make-sparse-keymap)))
    ;; Mostly taken from python-mode.el.
    (define-key map ":" 'python-electric-colon)
    (define-key map "\177" 'python-backspace)
    (define-key map "\C-c<" 'python-shift-left)
    (define-key map "\C-c>" 'python-shift-right)
    (define-key map "\C-c\C-k" 'python-mark-block)
    (define-key map "\C-c\C-d" 'python-pdbtrack-toggle-stack-tracking)
    (define-key map "\C-c\C-n" 'python-next-statement)
    (define-key map "\C-c\C-p" 'python-previous-statement)
    (define-key map "\C-c\C-u" 'python-beginning-of-block)
    (define-key map "\C-c\C-f" 'python-describe-symbol)
    (define-key map "\C-c\C-w" 'python-check)
    (define-key map "\C-c\C-v" 'python-check) ; a la sgml-mode
    (define-key map "\C-c\C-s" 'python-send-string)
    (define-key map [?\C-\M-x] 'python-send-defun)
    (define-key map "\C-c\C-r" 'python-send-region)
    (define-key map "\C-c\M-r" 'python-send-region-and-go)
    (define-key map "\C-c\C-c" 'python-send-buffer)
    (define-key map "\C-c\C-z" 'python-switch-to-python)
    (define-key map "\C-c\C-m" 'python-load-file)
    (define-key map "\C-c\C-l" 'python-load-file) ; a la cmuscheme
    (substitute-key-definition 'complete-symbol 'completion-at-point
			       map global-map)
    (define-key map "\C-c\C-i" 'python-find-imports)
    (define-key map "\C-c\C-t" 'python-expand-template)
    (easy-menu-define python-menu map "Python Mode menu"
      `("Python"
	:help "Python-specific Features"
	["Shift region left" python-shift-left :active mark-active
	 :help "Shift by a single indentation step"]
	["Shift region right" python-shift-right :active mark-active
	 :help "Shift by a single indentation step"]
	"-"
	["Mark block" python-mark-block
	 :help "Mark innermost block around point"]
	["Mark def/class" mark-defun
	 :help "Mark innermost definition around point"]
	"-"
	["Start of block" python-beginning-of-block
	 :help "Go to start of innermost definition around point"]
	["End of block" python-end-of-block
	 :help "Go to end of innermost definition around point"]
	["Start of def/class" beginning-of-defun
	 :help "Go to start of innermost definition around point"]
	["End of def/class" end-of-defun
	 :help "Go to end of innermost definition around point"]
	"-"
	("Templates..."
	 :help "Expand templates for compound statements"
	 :filter (lambda (&rest junk)
                   (abbrev-table-menu python-mode-abbrev-table)))
	"-"
	["Start interpreter" run-python
	 :help "Run `inferior' Python in separate buffer"]
	["Import/reload file" python-load-file
	 :help "Load into inferior Python session"]
	["Eval buffer" python-send-buffer
	 :help "Evaluate buffer en bloc in inferior Python session"]
	["Eval region" python-send-region :active mark-active
	 :help "Evaluate region en bloc in inferior Python session"]
	["Eval def/class" python-send-defun
	 :help "Evaluate current definition in inferior Python session"]
	["Switch to interpreter" python-switch-to-python
	 :help "Switch to inferior Python buffer"]
	["Set default process" python-set-proc
	 :help "Make buffer's inferior process the default"
	 :active (buffer-live-p python-buffer)]
	["Check file" python-check :help "Run pychecker"]
	["Debugger" pdb :help "Run pdb under GUD"]
	"-"
	["Help on symbol" python-describe-symbol
	 :help "Use pydoc on symbol at point"]
	["Complete symbol" completion-at-point
	 :help "Complete (qualified) symbol before point"]
	["Find function" python-find-function
	 :help "Try to find source definition of function at point"]
	["Update imports" python-find-imports
	 :help "Update list of top-level imports for completion"]))
    map))
;; Fixme: add toolbar stuff for useful things like symbol help, send
;; region, at least.  (Shouldn't be specific to Python, obviously.)
;; eric has items including: (un)indent, (un)comment, restart script,
;; run script, debug script; also things for profiling, unit testing.

(defvar python-mode-syntax-table
  (let ((table (make-syntax-table)))
    ;; Give punctuation syntax to ASCII that normally has symbol
    ;; syntax or has word syntax and isn't a letter.
    (let ((symbol (string-to-syntax "_"))
	  (sst (standard-syntax-table)))
      (dotimes (i 128)
	(unless (= i ?_)
	  (if (equal symbol (aref sst i))
	      (modify-syntax-entry i "." table)))))
    (modify-syntax-entry ?$ "." table)
    (modify-syntax-entry ?% "." table)
    ;; exceptions
    (modify-syntax-entry ?# "<" table)
    (modify-syntax-entry ?\n ">" table)
    (modify-syntax-entry ?' "\"" table)
    (modify-syntax-entry ?` "$" table)
    table))

;;;; Utility stuff

(defsubst python-in-string/comment ()
  "Return non-nil if point is in a Python literal (a comment or string)."
  ;; We don't need to save the match data.
  (nth 8 (syntax-ppss)))

(defconst python-space-backslash-table
  (let ((table (copy-syntax-table python-mode-syntax-table)))
    (modify-syntax-entry ?\\ " " table)
    table)
  "`python-mode-syntax-table' with backslash given whitespace syntax.")

(defun python-skip-comments/blanks (&optional backward)
  "Skip comments and blank lines.
BACKWARD non-nil means go backwards, otherwise go forwards.
Backslash is treated as whitespace so that continued blank lines
are skipped.  Doesn't move out of comments -- should be outside
or at end of line."
  (let ((arg (if backward
		 ;; If we're in a comment (including on the trailing
		 ;; newline), forward-comment doesn't move backwards out
		 ;; of it.  Don't set the syntax table round this bit!
		 (let ((syntax (syntax-ppss)))
		   (if (nth 4 syntax)
		       (goto-char (nth 8 syntax)))
		   (- (point-max)))
	       (point-max))))
    (with-syntax-table python-space-backslash-table
      (forward-comment arg))))

(defun python-backslash-continuation-line-p ()
  "Non-nil if preceding line ends with backslash that is not in a comment."
  (and (eq ?\\ (char-before (line-end-position 0)))
       (not (syntax-ppss-context (syntax-ppss)))))

(defun python-continuation-line-p ()
  "Return non-nil if current line continues a previous one.
The criteria are that the previous line ends in a backslash outside
comments and strings, or that point is within brackets/parens."
  (or (python-backslash-continuation-line-p)
      (let ((depth (syntax-ppss-depth
		    (save-excursion ; syntax-ppss with arg changes point
		      (syntax-ppss (line-beginning-position))))))
	(or (> depth 0)
	    (if (< depth 0)	  ; Unbalanced brackets -- act locally
		(save-excursion
		  (condition-case ()
		      (progn (backward-up-list) t) ; actually within brackets
		    (error nil))))))))

(defun python-comment-line-p ()
  "Return non-nil if and only if current line has only a comment."
  (save-excursion
    (end-of-line)
    (when (eq 'comment (syntax-ppss-context (syntax-ppss)))
      (back-to-indentation)
      (looking-at (rx (or (syntax comment-start) line-end))))))

(defun python-blank-line-p ()
  "Return non-nil if and only if current line is blank."
  (save-excursion
    (beginning-of-line)
    (looking-at "\\s-*$")))

(defun python-beginning-of-string ()
  "Go to beginning of string around point.
Do nothing if not in string."
  (let ((state (syntax-ppss)))
    (when (eq 'string (syntax-ppss-context state))
      (goto-char (nth 8 state)))))

(defun python-open-block-statement-p (&optional bos)
  "Return non-nil if statement at point opens a block.
BOS non-nil means point is known to be at beginning of statement."
  (save-excursion
    (unless bos (python-beginning-of-statement))
    (looking-at (rx (and (or "if" "else" "elif" "while" "for" "def"
			     "class" "try" "except" "finally" "with")
			 symbol-end)))))

(defun python-close-block-statement-p (&optional bos)
  "Return non-nil if current line is a statement closing a block.
BOS non-nil means point is at beginning of statement.
The criteria are that the line isn't a comment or in string and
 starts with keyword `raise', `break', `continue' or `pass'."
  (save-excursion
    (unless bos (python-beginning-of-statement))
    (back-to-indentation)
    (looking-at (rx (or "return" "raise" "break" "continue" "pass")
		    symbol-end))))

(defun python-outdent-p ()
  "Return non-nil if current line should outdent a level."
  (save-excursion
    (back-to-indentation)
    (and (looking-at (rx (and (or "else" "finally" "except" "elif")
			      symbol-end)))
	 (not (python-in-string/comment))
	 ;; Ensure there's a previous statement and move to it.
	 (zerop (python-previous-statement))
	 (not (python-close-block-statement-p t))
	 ;; Fixme: check this
	 (not (python-open-block-statement-p)))))

;;;; Indentation.

(defcustom python-indent 4
  "Number of columns for a unit of indentation in Python mode.
See also `\\[python-guess-indent]'"
  :group 'python
  :type 'integer)
(put 'python-indent 'safe-local-variable 'integerp)

(defcustom python-guess-indent t
  "Non-nil means Python mode guesses `python-indent' for the buffer."
  :type 'boolean
  :group 'python)

(defcustom python-indent-string-contents t
  "Non-nil means indent contents of multi-line strings together.
This means indent them the same as the preceding non-blank line.
Otherwise preserve their indentation.

This only applies to `doc' strings, i.e. those that form statements;
the indentation is preserved in others."
  :type '(choice (const :tag "Align with preceding" t)
		 (const :tag "Preserve indentation" nil))
  :group 'python)

(defcustom python-honour-comment-indentation nil
  "Non-nil means indent relative to preceding comment line.
Only do this for comments where the leading comment character is
followed by space.  This doesn't apply to comment lines, which
are always indented in lines with preceding comments."
  :type 'boolean
  :group 'python)

(defcustom python-continuation-offset 4
  "Number of columns of additional indentation for continuation lines.
Continuation lines follow a backslash-terminated line starting a
statement."
  :group 'python
  :type 'integer)


(defcustom python-pdbtrack-do-tracking-p t
  "*Controls whether the pdbtrack feature is enabled or not.

When non-nil, pdbtrack is enabled in all comint-based buffers,
e.g. shell interaction buffers and the *Python* buffer.

When using pdb to debug a Python program, pdbtrack notices the
pdb prompt and presents the line in the source file where the
program is stopped in a pop-up buffer.  It's similar to what
gud-mode does for debugging C programs with gdb, but without
having to restart the program."
  :type 'boolean
  :group 'python)
(make-variable-buffer-local 'python-pdbtrack-do-tracking-p)

(defcustom python-pdbtrack-minor-mode-string " PDB"
  "*Minor-mode sign to be displayed when pdbtrack is active."
  :type 'string
  :group 'python)

;; Add a designator to the minor mode strings
(or (assq 'python-pdbtrack-is-tracking-p minor-mode-alist)
    (push '(python-pdbtrack-is-tracking-p python-pdbtrack-minor-mode-string)
	  minor-mode-alist))

(defcustom python-shell-prompt-alist
  '(("ipython" . "^In \\[[0-9]+\\]: *")
    (t . "^>>> "))
  "Alist of Python input prompts.
Each element has the form (PROGRAM . REGEXP), where PROGRAM is
the value of `python-python-command' for the python process and
REGEXP is a regular expression matching the Python prompt.
PROGRAM can also be t, which specifies the default when no other
element matches `python-python-command'."
  :type 'string
  :group 'python
  :version "24.1")

(defcustom python-shell-continuation-prompt-alist
  '(("ipython" . "^   [.][.][.]+: *")
    (t . "^[.][.][.] "))
  "Alist of Python continued-line prompts.
Each element has the form (PROGRAM . REGEXP), where PROGRAM is
the value of `python-python-command' for the python process and
REGEXP is a regular expression matching the Python prompt for
continued lines.
PROGRAM can also be t, which specifies the default when no other
element matches `python-python-command'."
  :type 'string
  :group 'python
  :version "24.1")

(defvar python-pdbtrack-is-tracking-p nil)

(defconst python-pdbtrack-stack-entry-regexp
  "^> \\(.*\\)(\\([0-9]+\\))\\([?a-zA-Z0-9_<>]+\\)()"
  "Regular expression pdbtrack uses to find a stack trace entry.")

(defconst python-pdbtrack-input-prompt "\n[(<]*[Ii]?[Pp]db[>)]+ "
  "Regular expression pdbtrack uses to recognize a pdb prompt.")

(defconst python-pdbtrack-track-range 10000
  "Max number of characters from end of buffer to search for stack entry.")

(defun python-guess-indent ()
  "Guess step for indentation of current buffer.
Set `python-indent' locally to the value guessed."
  (interactive)
  (save-excursion
    (save-restriction
      (widen)
      (goto-char (point-min))
      (let (done indent)
	(while (and (not done) (not (eobp)))
	  (when (and (re-search-forward (rx ?: (0+ space)
					    (or (syntax comment-start)
						line-end))
					nil 'move)
		     (python-open-block-statement-p))
	    (save-excursion
	      (python-beginning-of-statement)
	      (let ((initial (current-indentation)))
		(if (zerop (python-next-statement))
		    (setq indent (- (current-indentation) initial)))
		(if (and indent (>= indent 2) (<= indent 8)) ; sanity check
		    (setq done t))))))
	(when done
	  (when (/= indent (default-value 'python-indent))
	    (set (make-local-variable 'python-indent) indent)
	    (unless (= tab-width python-indent)
	      (setq indent-tabs-mode nil)))
	  indent)))))

;; Alist of possible indentations and start of statement they would
;; close.  Used in indentation cycling (below).
(defvar python-indent-list nil
  "Internal use.")
;; Length of the above
(defvar python-indent-list-length nil
  "Internal use.")
;; Current index into the alist.
(defvar python-indent-index nil
  "Internal use.")

(defun python-calculate-indentation ()
  "Calculate Python indentation for line at point."
  (setq python-indent-list nil
	python-indent-list-length 1)
  (save-excursion
    (beginning-of-line)
    (let ((syntax (syntax-ppss))
	  start)
      (cond
       ((eq 'string (syntax-ppss-context syntax)) ; multi-line string
	(if (not python-indent-string-contents)
	    (current-indentation)
	  ;; Only respect `python-indent-string-contents' in doc
	  ;; strings (defined as those which form statements).
	  (if (not (save-excursion
		     (python-beginning-of-statement)
		     (looking-at (rx (or (syntax string-delimiter)
					 (syntax string-quote))))))
	      (current-indentation)
	    ;; Find indentation of preceding non-blank line within string.
	    (setq start (nth 8 syntax))
	    (forward-line -1)
	    (while (and (< start (point)) (looking-at "\\s-*$"))
	      (forward-line -1))
	    (current-indentation))))
       ((python-continuation-line-p)   ; after backslash, or bracketed
	(let ((point (point))
	      (open-start (cadr syntax))
	      (backslash (python-backslash-continuation-line-p))
	      (colon (eq ?: (char-before (1- (line-beginning-position))))))
	  (if open-start
	      ;; Inside bracketed expression.
	      (progn
		(goto-char (1+ open-start))
		;; Look for first item in list (preceding point) and
		;; align with it, if found.
		(if (with-syntax-table python-space-backslash-table
		      (let ((parse-sexp-ignore-comments t))
			(condition-case ()
			    (progn (forward-sexp)
				   (backward-sexp)
				   (< (point) point))
			  (error nil))))
		    ;; Extra level if we're backslash-continued or
		    ;; following a key.
		    (if (or backslash colon)
			(+ python-indent (current-column))
			(current-column))
		  ;; Otherwise indent relative to statement start, one
		  ;; level per bracketing level.
		  (goto-char (1+ open-start))
		  (python-beginning-of-statement)
		  (+ (current-indentation) (* (car syntax) python-indent))))
	    ;; Otherwise backslash-continued.
	    (forward-line -1)
	    (if (python-continuation-line-p)
		;; We're past first continuation line.  Align with
		;; previous line.
		(current-indentation)
	      ;; First continuation line.  Indent one step, with an
	      ;; extra one if statement opens a block.
	      (python-beginning-of-statement)
	      (+ (current-indentation) python-continuation-offset
		 (if (python-open-block-statement-p t)
		     python-indent
		   0))))))
       ((bobp) 0)
       ;; Fixme: Like python-mode.el; not convinced by this.
       ((looking-at (rx (0+ space) (syntax comment-start)
			(not (any " \t\n")))) ; non-indentable comment
	(current-indentation))
       ((and python-honour-comment-indentation
	     ;; Back over whitespace, newlines, non-indentable comments.
	     (catch 'done
	       (while (cond ((bobp) nil)
			    ((not (forward-comment -1))
			     nil)	; not at comment start
			    ;; Now at start of comment -- trailing one?
			    ((/= (current-column) (current-indentation))
			     nil)
			    ;; Indentable comment, like python-mode.el?
			    ((and (looking-at (rx (syntax comment-start)
						  (or space line-end)))
				  (/= 0 (current-column)))
			     (throw 'done (current-column)))
			    ;; Else skip it (loop).
			    (t))))))
       (t
	(python-indentation-levels)
	;; Prefer to indent comments with an immediately-following
	;; statement, e.g.
	;;       ...
	;;   # ...
	;;   def ...
	(when (and (> python-indent-list-length 1)
		   (python-comment-line-p))
	  (forward-line)
	  (unless (python-comment-line-p)
	    (let ((elt (assq (current-indentation) python-indent-list)))
	      (setq python-indent-list
		    (nconc (delete elt python-indent-list)
			   (list elt))))))
	(caar (last python-indent-list)))))))

;;;; Cycling through the possible indentations with successive TABs.

;; These don't need to be buffer-local since they're only relevant
;; during a cycle.

(defun python-initial-text ()
  "Text of line following indentation and ignoring any trailing comment."
  (save-excursion
    (buffer-substring (progn
			(back-to-indentation)
			(point))
		      (progn
			(end-of-line)
			(forward-comment -1)
			(point)))))

(defconst python-block-pairs
  '(("else" "if" "elif" "while" "for" "try" "except")
    ("elif" "if" "elif")
    ("except" "try" "except")
    ("finally" "else" "try" "except"))
  "Alist of keyword matches.
The car of an element is a keyword introducing a statement which
can close a block opened by a keyword in the cdr.")

(defun python-first-word ()
  "Return first word (actually symbol) on the line."
  (save-excursion
    (back-to-indentation)
    (current-word t)))

(defun python-indentation-levels ()
  "Return a list of possible indentations for this line.
It is assumed not to be a continuation line or in a multi-line string.
Includes the default indentation and those which would close all
enclosing blocks.  Elements of the list are actually pairs:
\(INDENTATION . TEXT), where TEXT is the initial text of the
corresponding block opening (or nil)."
  (save-excursion
    (let ((initial "")
	  levels indent)
      ;; Only one possibility immediately following a block open
      ;; statement, assuming it doesn't have a `suite' on the same line.
      (cond
       ((save-excursion (and (python-previous-statement)
			     (python-open-block-statement-p t)
			     (setq indent (current-indentation))
			     ;; Check we don't have something like:
			     ;;   if ...: ...
			     (if (progn (python-end-of-statement)
					(python-skip-comments/blanks t)
					(eq ?: (char-before)))
				 (setq indent (+ python-indent indent)))))
	(push (cons indent initial) levels))
       ;; Only one possibility for comment line immediately following
       ;; another.
       ((save-excursion
	  (when (python-comment-line-p)
	    (forward-line -1)
	    (if (python-comment-line-p)
		(push (cons (current-indentation) initial) levels)))))
       ;; Fixme: Maybe have a case here which indents (only) first
       ;; line after a lambda.
       (t
	(let ((start (car (assoc (python-first-word) python-block-pairs))))
	  (python-previous-statement)
	  ;; Is this a valid indentation for the line of interest?
	  (unless (or (if start		; potentially only outdentable
			  ;; Check for things like:
			  ;;   if ...: ...
			  ;;   else ...:
			  ;; where the second line need not be outdented.
			  (not (member (python-first-word)
				       (cdr (assoc start
						   python-block-pairs)))))
		      ;; Not sensible to indent to the same level as
		      ;; previous `return' &c.
		      (python-close-block-statement-p))
	    (push (cons (current-indentation) (python-initial-text))
		  levels))
	  (while (python-beginning-of-block)
	    (when (or (not start)
		      (member (python-first-word)
			      (cdr (assoc start python-block-pairs))))
	      (push (cons (current-indentation) (python-initial-text))
		    levels))))))
      (prog1 (or levels (setq levels '((0 . ""))))
	(setq python-indent-list levels
	      python-indent-list-length (length python-indent-list))))))

;; This is basically what `python-indent-line' would be if we didn't
;; do the cycling.
(defun python-indent-line-1 (&optional leave)
  "Subroutine of `python-indent-line'.
Does non-repeated indentation.  LEAVE non-nil means leave
indentation if it is valid, i.e. one of the positions returned by
`python-calculate-indentation'."
  (let ((target (python-calculate-indentation))
	(pos (- (point-max) (point))))
    (if (or (= target (current-indentation))
	    ;; Maybe keep a valid indentation.
	    (and leave python-indent-list
		 (assq (current-indentation) python-indent-list)))
	(if (< (current-column) (current-indentation))
	    (back-to-indentation))
      (beginning-of-line)
      (delete-horizontal-space)
      (indent-to target)
      (if (> (- (point-max) pos) (point))
	  (goto-char (- (point-max) pos))))))

(defun python-indent-line ()
  "Indent current line as Python code.
When invoked via `indent-for-tab-command', cycle through possible
indentations for current line.  The cycle is broken by a command
different from `indent-for-tab-command', i.e. successive TABs do
the cycling."
  (interactive)
  (if (and (eq this-command 'indent-for-tab-command)
	   (eq last-command this-command))
      (if (= 1 python-indent-list-length)
	  (message "Sole indentation")
	(progn (setq python-indent-index
		     (% (1+ python-indent-index) python-indent-list-length))
	       (beginning-of-line)
	       (delete-horizontal-space)
	       (indent-to (car (nth python-indent-index python-indent-list)))
	       (if (python-block-end-p)
		   (let ((text (cdr (nth python-indent-index
					 python-indent-list))))
		     (if text
			 (message "Closes: %s" text))))))
    (python-indent-line-1)
    (setq python-indent-index (1- python-indent-list-length))))

(defun python-indent-region (start end)
  "`indent-region-function' for Python.
Leaves validly-indented lines alone, i.e. doesn't indent to
another valid position."
  (save-excursion
    (goto-char end)
    (setq end (point-marker))
    (goto-char start)
    (or (bolp) (forward-line 1))
    (while (< (point) end)
      (or (and (bolp) (eolp))
	  (python-indent-line-1 t))
      (forward-line 1))
    (move-marker end nil)))

(defun python-block-end-p ()
  "Non-nil if this is a line in a statement closing a block,
or a blank line indented to where it would close a block."
  (and (not (python-comment-line-p))
       (or (python-close-block-statement-p t)
	   (< (current-indentation)
	      (save-excursion
		(python-previous-statement)
		(current-indentation))))))

;;;; Movement.

;; Fixme:  Define {for,back}ward-sexp-function?  Maybe skip units like
;; block, statement, depending on context.

(defun python-beginning-of-defun ()
  "`beginning-of-defun-function' for Python.
Finds beginning of innermost nested class or method definition.
Returns the name of the definition found at the end, or nil if
reached start of buffer."
  (let ((ci (current-indentation))
	(def-re (rx line-start (0+ space) (or "def" "class") (1+ space)
		    (group (1+ (or word (syntax symbol))))))
	found lep) ;; def-line
    (if (python-comment-line-p)
	(setq ci most-positive-fixnum))
    (while (and (not (bobp)) (not found))
      ;; Treat bol at beginning of function as outside function so
      ;; that successive C-M-a makes progress backwards.
      ;;(setq def-line (looking-at def-re))
      (unless (bolp) (end-of-line))
      (setq lep (line-end-position))
      (if (and (re-search-backward def-re nil 'move)
	       ;; Must be less indented or matching top level, or
	       ;; equally indented if we started on a definition line.
	       (let ((in (current-indentation)))
		 (or (and (zerop ci) (zerop in))
		     (= lep (line-end-position)) ; on initial line
		     ;; Not sure why it was like this -- fails in case of
		     ;; last internal function followed by first
		     ;; non-def statement of the main body.
;; 		     (and def-line (= in ci))
		     (= in ci)
		     (< in ci)))
	       (not (python-in-string/comment)))
	  (setq found t)))
    found))

(defun python-end-of-defun ()
  "`end-of-defun-function' for Python.
Finds end of innermost nested class or method definition."
  (let ((orig (point))
	(pattern (rx line-start (0+ space) (or "def" "class") space)))
    ;; Go to start of current block and check whether it's at top
    ;; level.  If it is, and not a block start, look forward for
    ;; definition statement.
    (when (python-comment-line-p)
      (end-of-line)
      (forward-comment most-positive-fixnum))
    (if (not (python-open-block-statement-p))
	(python-beginning-of-block))
    (if (zerop (current-indentation))
	(unless (python-open-block-statement-p)
	  (while (and (re-search-forward pattern nil 'move)
		      (python-in-string/comment))) ; just loop
	  (unless (eobp)
	    (beginning-of-line)))
      ;; Don't move before top-level statement that would end defun.
      (end-of-line)
      (python-beginning-of-defun))
    ;; If we got to the start of buffer, look forward for
    ;; definition statement.
    (if (and (bobp) (not (looking-at "def\\|class")))
	(while (and (not (eobp))
		    (re-search-forward pattern nil 'move)
		    (python-in-string/comment)))) ; just loop
    ;; We're at a definition statement (or end-of-buffer).
    (unless (eobp)
      (python-end-of-block)
      ;; Count trailing space in defun (but not trailing comments).
      (skip-syntax-forward " >")
      (unless (eobp)			; e.g. missing final newline
	(beginning-of-line)))
    ;; Catch pathological cases like this, where the beginning-of-defun
    ;; skips to a definition we're not in:
    ;; if ...:
    ;;     ...
    ;; else:
    ;;     ...  # point here
    ;;     ...
    ;;     def ...
    (if (< (point) orig)
	(goto-char (point-max)))))

(defun python-beginning-of-statement ()
  "Go to start of current statement.
Accounts for continuation lines, multi-line strings, and
multi-line bracketed expressions."
  (while
      (if (python-backslash-continuation-line-p)
          (progn (forward-line -1) t)
        (beginning-of-line)
        (or (python-beginning-of-string)
            (python-skip-out))))
  (back-to-indentation))

(defun python-skip-out (&optional forward syntax)
  "Skip out of any nested brackets.
Skip forward if FORWARD is non-nil, else backward.
If SYNTAX is non-nil it is the state returned by `syntax-ppss' at point.
Return non-nil if and only if skipping was done."
  ;; FIXME: Use syntax-ppss-toplevel-pos.
  (let ((depth (syntax-ppss-depth (or syntax (syntax-ppss))))
	(forward (if forward -1 1)))
    (unless (zerop depth)
      (if (> depth 0)
	  ;; Skip forward out of nested brackets.
	  (condition-case ()		; beware invalid syntax
	      (progn (backward-up-list (* forward depth)) t)
	    (error nil))
	;; Invalid syntax (too many closed brackets).
	;; Skip out of as many as possible.
	(let (done)
	  (while (condition-case ()
		     (progn (backward-up-list forward)
			    (setq done t))
		   (error nil)))
	  done)))))

(defun python-end-of-statement ()
  "Go to the end of the current statement and return point.
Usually this is the start of the next line, but if this is a
multi-line statement we need to skip over the continuation lines.
On a comment line, go to end of line."
  (end-of-line)
  (while (let (comment)
	   ;; Move past any enclosing strings and sexps, or stop if
	   ;; we're in a comment.
	   (while (let ((s (syntax-ppss)))
		    (cond ((eq 'comment (syntax-ppss-context s))
			   (setq comment t)
			   nil)
			  ((eq 'string (syntax-ppss-context s))
			   ;; Go to start of string and skip it.
                           (let ((pos (point)))
                             (goto-char (nth 8 s))
                             (condition-case () ; beware invalid syntax
                                 (progn (forward-sexp) t)
                               ;; If there's a mismatched string, make sure
                               ;; we still overall move *forward*.
                               (error (goto-char pos) (end-of-line)))))
			  ((python-skip-out t s))))
	     (end-of-line))
	   (and (not comment)
		(not (eobp))
		(eq ?\\ (char-before)))) ; Line continued?
    (end-of-line 2))                     ; Try next line.
  (point))

(defun python-previous-statement (&optional count)
  "Go to start of previous statement.
With argument COUNT, do it COUNT times.  Stop at beginning of buffer.
Return count of statements left to move."
  (interactive "p")
  (unless count (setq count 1))
  (if (< count 0)
      (python-next-statement (- count))
    (python-beginning-of-statement)
    (while (and (> count 0) (not (bobp)))
      (python-skip-comments/blanks t)
      (python-beginning-of-statement)
      (unless (bobp) (setq count (1- count))))
    count))

(defun python-next-statement (&optional count)
  "Go to start of next statement.
With argument COUNT, do it COUNT times.  Stop at end of buffer.
Return count of statements left to move."
  (interactive "p")
  (unless count (setq count 1))
  (if (< count 0)
      (python-previous-statement (- count))
    (beginning-of-line)
    (let (bogus)
      (while (and (> count 0) (not (eobp)) (not bogus))
	(python-end-of-statement)
	(python-skip-comments/blanks)
	(if (eq 'string (syntax-ppss-context (syntax-ppss)))
	    (setq bogus t)
	  (unless (eobp)
	    (setq count (1- count))))))
    count))

(defun python-beginning-of-block (&optional arg)
  "Go to start of current block.
With numeric arg, do it that many times.  If ARG is negative, call
`python-end-of-block' instead.
If point is on the first line of a block, use its outer block.
If current statement is in column zero, don't move and return nil.
Otherwise return non-nil."
  (interactive "p")
  (unless arg (setq arg 1))
  (cond
   ((zerop arg))
   ((< arg 0) (python-end-of-block (- arg)))
   (t
    (let ((point (point)))
      (if (or (python-comment-line-p)
	      (python-blank-line-p))
	  (python-skip-comments/blanks t))
      (python-beginning-of-statement)
      (let ((ci (current-indentation)))
	(if (zerop ci)
	    (not (goto-char point))	; return nil
	  ;; Look upwards for less indented statement.
	  (if (catch 'done
;;; This is slower than the below.
;;; 	  (while (zerop (python-previous-statement))
;;; 	    (when (and (< (current-indentation) ci)
;;; 		       (python-open-block-statement-p t))
;;; 	      (beginning-of-line)
;;; 	      (throw 'done t)))
		(while (and (zerop (forward-line -1)))
		  (when (and (< (current-indentation) ci)
			     (not (python-comment-line-p))
			     ;; Move to beginning to save effort in case
			     ;; this is in string.
			     (progn (python-beginning-of-statement) t)
			     (python-open-block-statement-p t))
		    (beginning-of-line)
		    (throw 'done t)))
		(not (goto-char point))) ; Failed -- return nil
	      (python-beginning-of-block (1- arg)))))))))

(defun python-end-of-block (&optional arg)
  "Go to end of current block.
With numeric arg, do it that many times.  If ARG is negative,
call `python-beginning-of-block' instead.
If current statement is in column zero and doesn't open a block,
don't move and return nil.  Otherwise return t."
  (interactive "p")
  (unless arg (setq arg 1))
  (if (< arg 0)
      (python-beginning-of-block (- arg))
    (while (and (> arg 0)
		(let* ((point (point))
		       (_ (if (python-comment-line-p)
			      (python-skip-comments/blanks t)))
		       (ci (current-indentation))
		       (open (python-open-block-statement-p)))
		  (if (and (zerop ci) (not open))
		      (not (goto-char point))
		    (catch 'done
		      (while (zerop (python-next-statement))
			(when (or (and open (<= (current-indentation) ci))
				  (< (current-indentation) ci))
			  (python-skip-comments/blanks t)
			  (beginning-of-line 2)
			  (throw 'done t)))))))
      (setq arg (1- arg)))
    (zerop arg)))

(defvar python-which-func-length-limit 40
  "Non-strict length limit for `python-which-func' output.")

(defun python-which-func ()
  (let ((function-name (python-current-defun python-which-func-length-limit)))
    (set-text-properties 0 (length function-name) nil function-name)
    function-name))


;;;; Imenu.

;; For possibly speeding this up, here's the top of the ELP profile
;; for rescanning pydoc.py (2.2k lines, 90kb):
;; Function Name                         Call Count  Elapsed Time  Average Time
;; ====================================  ==========  =============  ============
;; python-imenu-create-index             156         2.430906      0.0155827307
;; python-end-of-defun                   155         1.2718260000  0.0082053290
;; python-end-of-block                   155         1.1898689999  0.0076765741
;; python-next-statement                 2970        1.024717      0.0003450225
;; python-end-of-statement               2970        0.4332190000  0.0001458649
;; python-beginning-of-defun             265         0.0918479999  0.0003465962
;; python-skip-comments/blanks           3125        0.0753319999  2.410...e-05

(defvar python-recursing)
(defun python-imenu-create-index ()
  "`imenu-create-index-function' for Python.

Makes nested Imenu menus from nested `class' and `def' statements.
The nested menus are headed by an item referencing the outer
definition; it has a space prepended to the name so that it sorts
first with `imenu--sort-by-name' (though, unfortunately, sub-menus
precede it)."
  (unless (boundp 'python-recursing)	; dynamically bound below
    ;; Normal call from Imenu.
    (goto-char (point-min))
    ;; Without this, we can get an infloop if the buffer isn't all
    ;; fontified.  I guess this is really a bug in syntax.el.  OTOH,
    ;; _with_ this, imenu doesn't immediately work; I can't figure out
    ;; what's going on, but it must be something to do with timers in
    ;; font-lock.
    ;; This can't be right, especially not when jit-lock is not used.  --Stef
    ;; (unless (get-text-property (1- (point-max)) 'fontified)
    ;;   (font-lock-fontify-region (point-min) (point-max)))
    )
  (let (index-alist)			; accumulated value to return
    (while (re-search-forward
	    (rx line-start (0+ space)	; leading space
		(or (group "def") (group "class"))	   ; type
		(1+ space) (group (1+ (or word ?_))))	   ; name
	    nil t)
      (unless (python-in-string/comment)
	(let ((pos (match-beginning 0))
	      (name (match-string-no-properties 3)))
	  (if (match-beginning 2)	; def or class?
	      (setq name (concat "class " name)))
	  (save-restriction
	    (narrow-to-defun)
	    (let* ((python-recursing t)
		   (sublist (python-imenu-create-index)))
	      (if sublist
		  (progn (push (cons (concat " " name) pos) sublist)
			 (push (cons name sublist) index-alist))
		(push (cons name pos) index-alist)))))))
    (unless (boundp 'python-recursing)
      ;; Look for module variables.
      (let (vars)
	(goto-char (point-min))
	(while (re-search-forward
		(rx line-start (group (1+ (or word ?_))) (0+ space) "=")
		nil t)
	  (unless (python-in-string/comment)
	    (push (cons (match-string 1) (match-beginning 1))
		  vars)))
	(setq index-alist (nreverse index-alist))
	(if vars
	    (push (cons "Module variables"
			(nreverse vars))
		  index-alist))))
    index-alist))

;;;; `Electric' commands.

(defun python-electric-colon (arg)
  "Insert a colon and maybe outdent the line if it is a statement like `else'.
With numeric ARG, just insert that many colons.  With \\[universal-argument],
just insert a single colon."
  (interactive "*P")
  (self-insert-command (if (not (integerp arg)) 1 arg))
  (and (not arg)
       (eolp)
       (python-outdent-p)
       (not (python-in-string/comment))
       (> (current-indentation) (python-calculate-indentation))
       (python-indent-line)))		; OK, do it
(put 'python-electric-colon 'delete-selection t)

(defun python-backspace (arg)
  "Maybe delete a level of indentation on the current line.
Do so if point is at the end of the line's indentation outside
strings and comments.
Otherwise just call `backward-delete-char-untabify'.
Repeat ARG times."
  (interactive "*p")
  (if (or (/= (current-indentation) (current-column))
	  (bolp)
	  (python-continuation-line-p)
	  (python-in-string/comment))
      (backward-delete-char-untabify arg)
    ;; Look for the largest valid indentation which is smaller than
    ;; the current indentation.
    (let ((indent 0)
	  (ci (current-indentation))
	  (indents (python-indentation-levels))
	  initial)
      (dolist (x indents)
	(if (< (car x) ci)
	    (setq indent (max indent (car x)))))
      (setq initial (cdr (assq indent indents)))
      (if (> (length initial) 0)
	  (message "Closes %s" initial))
      (delete-horizontal-space)
      (indent-to indent))))
(put 'python-backspace 'delete-selection 'supersede)

;;;; pychecker

(defcustom python-check-command "pychecker --stdlib"
  "Command used to check a Python file."
  :type 'string
  :group 'python)

(defvar python-saved-check-command nil
  "Internal use.")

;; After `sgml-validate-command'.
(defun python-check (command)
  "Check a Python file (default current buffer's file).
Runs COMMAND, a shell command, as if by `compile'.
See `python-check-command' for the default."
  (interactive
   (list (read-string "Checker command: "
		      (or python-saved-check-command
			  (concat python-check-command " "
				  (let ((name (buffer-file-name)))
				    (if name
					(file-name-nondirectory name))))))))
  (set (make-local-variable 'python-saved-check-command) command)
  (require 'compile)                    ;To define compilation-* variables.
  (save-some-buffers (not compilation-ask-about-save) nil)
  (let ((compilation-error-regexp-alist
	 (cons '("(\\([^,]+\\), line \\([0-9]+\\))" 1 2)
	       compilation-error-regexp-alist)))
    (compilation-start command)))

;;;; Inferior mode stuff (following cmuscheme).

(defcustom python-python-command "python"
  "Shell command to run Python interpreter.
Any arguments can't contain whitespace."
  :group 'python
  :type 'string)

(defcustom python-jython-command "jython"
  "Shell command to run Jython interpreter.
Any arguments can't contain whitespace."
  :group 'python
  :type 'string)

(defvar python-command python-python-command
  "Actual command used to run Python.
May be `python-python-command' or `python-jython-command', possibly
modified by the user.  Additional arguments are added when the command
is used by `run-python' et al.")

(defvar python-buffer nil
  "*The current Python process buffer.

Commands that send text from source buffers to Python processes have
to choose a process to send to.  This is determined by buffer-local
value of `python-buffer'.  If its value in the current buffer,
i.e. both any local value and the default one, is nil, `run-python'
and commands that send to the Python process will start a new process.

Whenever \\[run-python] starts a new process, it resets the default
value of `python-buffer' to be the new process's buffer and sets the
buffer-local value similarly if the current buffer is in Python mode
or Inferior Python mode, so that source buffer stays associated with a
specific sub-process.

Use \\[python-set-proc] to set the default value from a buffer with a
local value.")
(make-variable-buffer-local 'python-buffer)

(defconst python-compilation-regexp-alist
  ;; FIXME: maybe these should move to compilation-error-regexp-alist-alist.
  ;;   The first already is (for CAML), but the second isn't.  Anyhow,
  ;;   these are specific to the inferior buffer.  -- fx
  `((,(rx line-start (1+ (any " \t")) "File \""
	  (group (1+ (not (any "\"<")))) ; avoid `<stdin>' &c
	  "\", line " (group (1+ digit)))
     1 2)
    (,(rx " in file " (group (1+ not-newline)) " on line "
	  (group (1+ digit)))
     1 2)
    ;; pdb stack trace
    (,(rx line-start "> " (group (1+ (not (any "(\"<"))))
	  "(" (group (1+ digit)) ")" (1+ (not (any "("))) "()")
     1 2))
  "`compilation-error-regexp-alist' for inferior Python.")

(defvar inferior-python-mode-map
  (let ((map (make-sparse-keymap)))
    ;; This will inherit from comint-mode-map.
    (define-key map "\C-c\C-l" 'python-load-file)
    (define-key map "\C-c\C-v" 'python-check)
    ;; Note that we _can_ still use these commands which send to the
    ;; Python process even at the prompt if we have a normal prompt,
    ;; i.e. '>>> ' and not '... '.  See the comment before
    ;; python-send-region.  Fixme: uncomment these if we address that.

    ;; (define-key map [(meta ?\t)] 'python-complete-symbol)
    ;; (define-key map "\C-c\C-f" 'python-describe-symbol)
    map))

(defvar inferior-python-mode-syntax-table
  (let ((st (make-syntax-table python-mode-syntax-table)))
    ;; Don't get confused by apostrophes in the process's output (e.g. if
    ;; you execute "help(os)").
    (modify-syntax-entry ?\' "." st)
    ;; Maybe we should do the same for double quotes?
    ;; (modify-syntax-entry ?\" "." st)
    st))

;; Autoloaded.
(declare-function compilation-shell-minor-mode "compile" (&optional arg))

(defvar python--prompt-regexp nil)

(defun python--set-prompt-regexp ()
  (let ((prompt  (cdr-safe (or (assoc python-python-command
				      python-shell-prompt-alist)
			       (assq t python-shell-prompt-alist))))
	(cprompt (cdr-safe (or (assoc python-python-command
				      python-shell-continuation-prompt-alist)
			       (assq t python-shell-continuation-prompt-alist)))))
    (set (make-local-variable 'comint-prompt-regexp)
	 (concat "\\("
		 (mapconcat 'identity
			    (delq nil (list prompt cprompt "^([Pp]db) "))
			    "\\|")
		 "\\)"))
    (set (make-local-variable 'python--prompt-regexp) prompt)))

;; Fixme: This should inherit some stuff from `python-mode', but I'm
;; not sure how much: at least some keybindings, like C-c C-f;
;; syntax?; font-locking, e.g. for triple-quoted strings?
(define-derived-mode inferior-python-mode comint-mode "Inferior Python"
  "Major mode for interacting with an inferior Python process.
A Python process can be started with \\[run-python].

Hooks `comint-mode-hook' and `inferior-python-mode-hook' are run in
that order.

You can send text to the inferior Python process from other buffers
containing Python source.
 * \\[python-switch-to-python] switches the current buffer to the Python
    process buffer.
 * \\[python-send-region] sends the current region to the Python process.
 * \\[python-send-region-and-go] switches to the Python process buffer
    after sending the text.
For running multiple processes in multiple buffers, see `run-python' and
`python-buffer'.

\\{inferior-python-mode-map}"
  :group 'python
  (setq mode-line-process '(":%s"))
  (set (make-local-variable 'comint-input-filter) 'python-input-filter)
  (add-hook 'comint-preoutput-filter-functions #'python-preoutput-filter
	    nil t)
  (python--set-prompt-regexp)
  (set (make-local-variable 'compilation-error-regexp-alist)
       python-compilation-regexp-alist)
  (compilation-shell-minor-mode 1))

(defcustom inferior-python-filter-regexp "\\`\\s-*\\S-?\\S-?\\s-*\\'"
  "Input matching this regexp is not saved on the history list.
Default ignores all inputs of 0, 1, or 2 non-blank characters."
  :type 'regexp
  :group 'python)

(defcustom python-remove-cwd-from-path t
  "Whether to allow loading of Python modules from the current directory.
If this is non-nil, Emacs removes '' from sys.path when starting
an inferior Python process.  This is the default, for security
reasons, as it is easy for the Python process to be started
without the user's realization (e.g. to perform completion)."
  :type 'boolean
  :group 'python
  :version "23.3")

(defun python-input-filter (str)
  "`comint-input-filter' function for inferior Python.
Don't save anything for STR matching `inferior-python-filter-regexp'."
  (not (string-match inferior-python-filter-regexp str)))

;; Fixme: Loses with quoted whitespace.
(defun python-args-to-list (string)
  (let ((where (string-match "[ \t]" string)))
    (cond ((null where) (list string))
	  ((not (= where 0))
	   (cons (substring string 0 where)
		 (python-args-to-list (substring string (+ 1 where)))))
	  (t (let ((pos (string-match "[^ \t]" string)))
	       (if pos (python-args-to-list (substring string pos))))))))

(defvar python-preoutput-result nil
  "Data from last `_emacs_out' line seen by the preoutput filter.")

(defvar python-preoutput-continuation nil
  "If non-nil, funcall this when `python-preoutput-filter' sees `_emacs_ok'.")

(defvar python-preoutput-leftover nil)
(defvar python-preoutput-skip-next-prompt nil)

;; Using this stops us getting lines in the buffer like
;; >>> ... ... >>>
;; Also look for (and delete) an `_emacs_ok' string and call
;; `python-preoutput-continuation' if we get it.
(defun python-preoutput-filter (s)
  "`comint-preoutput-filter-functions' function: ignore prompts not at bol."
  (when python-preoutput-leftover
    (setq s (concat python-preoutput-leftover s))
    (setq python-preoutput-leftover nil))
  (let ((start 0)
        (res ""))
    ;; First process whole lines.
    (while (string-match "\n" s start)
      (let ((line (substring s start (setq start (match-end 0)))))
        ;; Skip prompt if needed.
        (when (and python-preoutput-skip-next-prompt
                   (string-match comint-prompt-regexp line))
          (setq python-preoutput-skip-next-prompt nil)
          (setq line (substring line (match-end 0))))
        ;; Recognize special _emacs_out lines.
        (if (and (string-match "\\`_emacs_out \\(.*\\)\n\\'" line)
                 (local-variable-p 'python-preoutput-result))
            (progn
              (setq python-preoutput-result (match-string 1 line))
              (set (make-local-variable 'python-preoutput-skip-next-prompt) t))
          (setq res (concat res line)))))
    ;; Then process the remaining partial line.
    (unless (zerop start) (setq s (substring s start)))
    (cond ((and (string-match comint-prompt-regexp s)
                ;; Drop this prompt if it follows an _emacs_out...
                (or python-preoutput-skip-next-prompt
                    ;; ... or if it's not gonna be inserted at BOL.
                    ;; Maybe we could be more selective here.
                    (if (zerop (length res))
                        (not (bolp))
                      (string-match ".\\'" res))))
           ;; The need for this seems to be system-dependent:
           ;; What is this all about, exactly?  --Stef
           ;; (if (and (eq ?. (aref s 0)))
           ;;     (accept-process-output (get-buffer-process (current-buffer)) 1))
           (setq python-preoutput-skip-next-prompt nil)
           res)
          ((let ((end (min (length "_emacs_out ") (length s))))
             (eq t (compare-strings s nil end "_emacs_out " nil end)))
           ;; The leftover string is a prefix of _emacs_out so we don't know
           ;; yet whether it's an _emacs_out or something else: wait until we
           ;; get more output so we can resolve this ambiguity.
           (set (make-local-variable 'python-preoutput-leftover) s)
           res)
          (t (concat res s)))))

(autoload 'comint-check-proc "comint")

(defvar python-version-checked nil)
(defun python-check-version (cmd)
  "Check that CMD runs a suitable version of Python."
  ;; Fixme:  Check on Jython.
  (unless (or python-version-checked
	      (equal 0 (string-match (regexp-quote python-python-command)
				     cmd)))
    (unless (shell-command-to-string cmd)
      (error "Can't run Python command `%s'" cmd))
    (let* ((res (shell-command-to-string
                 (concat cmd
                         " -c \"from sys import version_info;\
print version_info >= (2, 2) and version_info < (3, 0)\""))))
      (unless (string-match "True" res)
	(error "Only Python versions >= 2.2 and < 3.0 are supported")))
    (setq python-version-checked t)))

;;;###autoload
(defun run-python (&optional cmd noshow new)
  "Run an inferior Python process, input and output via buffer *Python*.
CMD is the Python command to run.  NOSHOW non-nil means don't
show the buffer automatically.

Interactively, a prefix arg means to prompt for the initial
Python command line (default is `python-command').

A new process is started if one isn't running attached to
`python-buffer', or if called from Lisp with non-nil arg NEW.
Otherwise, if a process is already running in `python-buffer',
switch to that buffer.

This command runs the hook `inferior-python-mode-hook' after
running `comint-mode-hook'.  Type \\[describe-mode] in the
process buffer for a list of commands.

By default, Emacs inhibits the loading of Python modules from the
current working directory, for security reasons.  To disable this
behavior, change `python-remove-cwd-from-path' to nil."
  (interactive (if current-prefix-arg
		   (list (read-string "Run Python: " python-command) nil t)
		 (list python-command)))
  (unless cmd (setq cmd python-command))
  (python-check-version cmd)
  (setq python-command cmd)
  ;; Fixme: Consider making `python-buffer' buffer-local as a buffer
  ;; (not a name) in Python buffers from which `run-python' &c is
  ;; invoked.  Would support multiple processes better.
  (when (or new (not (comint-check-proc python-buffer)))
    (with-current-buffer
	(let* ((cmdlist
		(append (python-args-to-list cmd) '("-i")
			(if python-remove-cwd-from-path
			    '("-c" "import sys; sys.path.remove('')"))))
	       (path (getenv "PYTHONPATH"))
	       (process-environment	; to import emacs.py
		(cons (concat "PYTHONPATH="
			      (if path (concat path path-separator))
			      data-directory)
		      process-environment))
               ;; If we use a pipe, Unicode characters are not printed
               ;; correctly (Bug#5794) and IPython does not work at
               ;; all (Bug#5390).
	       (process-connection-type t))
	  (apply 'make-comint-in-buffer "Python"
		 (generate-new-buffer "*Python*")
		 (car cmdlist) nil (cdr cmdlist)))
      (setq-default python-buffer (current-buffer))
      (setq python-buffer (current-buffer))
      (accept-process-output (get-buffer-process python-buffer) 5)
      (inferior-python-mode)
      ;; Load function definitions we need.
      ;; Before the preoutput function was used, this was done via -c in
      ;; cmdlist, but that loses the banner and doesn't run the startup
      ;; file.  The code might be inline here, but there's enough that it
      ;; seems worth putting in a separate file, and it's probably cleaner
      ;; to put it in a module.
      ;; Ensure we're at a prompt before doing anything else.
      (python-send-string "import emacs")
      ;; The following line was meant to ensure that we're at a prompt
      ;; before doing anything else.  However, this can cause Emacs to
      ;; hang waiting for a response, if that Python function fails
      ;; (i.e. raises an exception).
      ;; (python-send-receive "print '_emacs_out ()'")
      ))
  (if (derived-mode-p 'python-mode)
      (setq python-buffer (default-value 'python-buffer))) ; buffer-local
  ;; Without this, help output goes into the inferior python buffer if
  ;; the process isn't already running.
  (sit-for 1 t)        ;Should we use accept-process-output instead?  --Stef
  (unless noshow (pop-to-buffer python-buffer t)))

(defun python-send-command (command)
  "Like `python-send-string' but resets `compilation-shell-minor-mode'."
  (when (python-check-comint-prompt)
    (with-current-buffer (process-buffer (python-proc))
      (goto-char (point-max))
      (compilation-forget-errors)
      (python-send-string command)
      (setq compilation-last-buffer (current-buffer)))))

(defun python-send-region (start end)
  "Send the region to the inferior Python process."
  ;; The region is evaluated from a temporary file.  This avoids
  ;; problems with blank lines, which have different semantics
  ;; interactively and in files.  It also saves the inferior process
  ;; buffer filling up with interpreter prompts.  We need a Python
  ;; function to remove the temporary file when it has been evaluated
  ;; (though we could probably do it in Lisp with a Comint output
  ;; filter).  This function also catches exceptions and truncates
  ;; tracebacks not to mention the frame of the function itself.
  ;;
  ;; The `compilation-shell-minor-mode' parsing takes care of relating
  ;; the reference to the temporary file to the source.
  ;;
  ;; Fixme: Write a `coding' header to the temp file if the region is
  ;; non-ASCII.
  (interactive "r")
  (let* ((f (make-temp-file "py"))
	 (command
          ;; IPython puts the FakeModule module into __main__ so
          ;; emacs.eexecfile becomes useless.
          (if (string-match "^ipython" python-command)
              (format "execfile %S" f)
            (format "emacs.eexecfile(%S)" f)))
	 (orig-start (copy-marker start)))
    (when (save-excursion
	    (goto-char start)
	    (/= 0 (current-indentation))) ; need dummy block
      (save-excursion
	(goto-char orig-start)
	;; Wrong if we had indented code at buffer start.
	(set-marker orig-start (line-beginning-position 0)))
      (write-region "if True:\n" nil f nil 'nomsg))
    (write-region start end f t 'nomsg)
    (python-send-command command)
    (with-current-buffer (process-buffer (python-proc))
      ;; Tell compile.el to redirect error locations in file `f' to
      ;; positions past marker `orig-start'.  It has to be done *after*
      ;; `python-send-command''s call to `compilation-forget-errors'.
      (compilation-fake-loc orig-start f))))

(defun python-send-string (string)
  "Evaluate STRING in inferior Python process."
  (interactive "sPython command: ")
  (comint-send-string (python-proc) string)
  (unless (string-match "\n\\'" string)
    ;; Make sure the text is properly LF-terminated.
    (comint-send-string (python-proc) "\n"))
  (when (string-match "\n[ \t].*\n?\\'" string)
    ;; If the string contains a final indented line, add a second newline so
    ;; as to make sure we terminate the multiline instruction.
    (comint-send-string (python-proc) "\n")))

(defun python-send-buffer ()
  "Send the current buffer to the inferior Python process."
  (interactive)
  (python-send-region (point-min) (point-max)))

;; Fixme: Try to define the function or class within the relevant
;; module, not just at top level.
(defun python-send-defun ()
  "Send the current defun (class or method) to the inferior Python process."
  (interactive)
  (save-excursion (python-send-region (progn (beginning-of-defun) (point))
				      (progn (end-of-defun) (point)))))

(defun python-switch-to-python (eob-p)
  "Switch to the Python process buffer, maybe starting new process.
With prefix arg, position cursor at end of buffer."
  (interactive "P")
  (pop-to-buffer (process-buffer (python-proc)) t) ;Runs python if needed.
  (when eob-p
    (push-mark)
    (goto-char (point-max))))

(defun python-send-region-and-go (start end)
  "Send the region to the inferior Python process.
Then switch to the process buffer."
  (interactive "r")
  (python-send-region start end)
  (python-switch-to-python t))

(defcustom python-source-modes '(python-mode jython-mode)
  "Used to determine if a buffer contains Python source code.
If a file is loaded into a buffer that is in one of these major modes,
it is considered Python source by `python-load-file', which uses the
value to determine defaults."
  :type '(repeat function)
  :group 'python)

(defvar python-prev-dir/file nil
  "Caches (directory . file) pair used in the last `python-load-file' command.
Used for determining the default in the next one.")

(autoload 'comint-get-source "comint")

(defun python-load-file (file-name)
  "Load a Python file FILE-NAME into the inferior Python process.
If the file has extension `.py' import or reload it as a module.
Treating it as a module keeps the global namespace clean, provides
function location information for debugging, and supports users of
module-qualified names."
  (interactive (comint-get-source "Load Python file: " python-prev-dir/file
				  python-source-modes
				  t))	; because execfile needs exact name
  (comint-check-source file-name)     ; Check to see if buffer needs saving.
  (setq python-prev-dir/file (cons (file-name-directory file-name)
				   (file-name-nondirectory file-name)))
  (with-current-buffer (process-buffer (python-proc)) ;Runs python if needed.
    ;; Fixme: I'm not convinced by this logic from python-mode.el.
    (python-send-command
     (if (string-match "\\.py\\'" file-name)
	 (let ((module (file-name-sans-extension
			(file-name-nondirectory file-name))))
	   (format "emacs.eimport(%S,%S)"
		   module (file-name-directory file-name)))
       (format "execfile(%S)" file-name)))
    (message "%s loaded" file-name)))

(defun python-proc ()
  "Return the current Python process.
See variable `python-buffer'.  Starts a new process if necessary."
  ;; Fixme: Maybe should look for another active process if there
  ;; isn't one for `python-buffer'.
  (unless (comint-check-proc python-buffer)
    (run-python nil t))
  (get-buffer-process (if (derived-mode-p 'inferior-python-mode)
			  (current-buffer)
			python-buffer)))

(defun python-set-proc ()
  "Set the default value of `python-buffer' to correspond to this buffer.
If the current buffer has a local value of `python-buffer', set the
default (global) value to that.  The associated Python process is
the one that gets input from \\[python-send-region] et al when used
in a buffer that doesn't have a local value of `python-buffer'."
  (interactive)
  (if (local-variable-p 'python-buffer)
      (setq-default python-buffer python-buffer)
    (error "No local value of `python-buffer'")))

;;;; Context-sensitive help.

(defconst python-dotty-syntax-table
  (let ((table (make-syntax-table)))
    (set-char-table-parent table python-mode-syntax-table)
    (modify-syntax-entry ?. "_" table)
    table)
  "Syntax table giving `.' symbol syntax.
Otherwise inherits from `python-mode-syntax-table'.")

(defvar view-return-to-alist)
(eval-when-compile (autoload 'help-buffer "help-fns"))

(defvar python-imports)			; forward declaration

;; Fixme: Should this actually be used instead of info-look, i.e. be
;; bound to C-h S?  [Probably not, since info-look may work in cases
;; where this doesn't.]
(defun python-describe-symbol (symbol)
  "Get help on SYMBOL using `help'.
Interactively, prompt for symbol.

Symbol may be anything recognized by the interpreter's `help'
command -- e.g. `CALLS' -- not just variables in scope in the
interpreter.  This only works for Python version 2.2 or newer
since earlier interpreters don't support `help'.

In some cases where this doesn't find documentation, \\[info-lookup-symbol]
will."
  ;; Note that we do this in the inferior process, not a separate one, to
  ;; ensure the environment is appropriate.
  (interactive
   (let ((symbol (with-syntax-table python-dotty-syntax-table
		   (current-word)))
	 (enable-recursive-minibuffers t))
     (list (read-string (if symbol
			    (format "Describe symbol (default %s): " symbol)
			  "Describe symbol: ")
			nil nil symbol))))
  (if (equal symbol "") (error "No symbol"))
  ;; Ensure we have a suitable help buffer.
  ;; Fixme: Maybe process `Related help topics' a la help xrefs and
  ;; allow C-c C-f in help buffer.
  (let ((temp-buffer-show-hook		; avoid xref stuff
	 (lambda ()
	   (toggle-read-only 1)
	   (setq view-return-to-alist
		 (list (cons (selected-window) help-return-method))))))
    (with-output-to-temp-buffer (help-buffer)
      (with-current-buffer standard-output
 	;; Fixme: Is this actually useful?
	(help-setup-xref (list 'python-describe-symbol symbol)
			 (called-interactively-p 'interactive))
	(set (make-local-variable 'comint-redirect-subvert-readonly) t)
	(help-print-return-message))))
  (comint-redirect-send-command-to-process (format "emacs.ehelp(%S, %s)"
						   symbol python-imports)
   "*Help*" (python-proc) nil nil))

(add-to-list 'debug-ignored-errors "^No symbol")

(defun python-send-receive (string)
  "Send STRING to inferior Python (if any) and return result.
The result is what follows `_emacs_out' in the output.
This is a no-op if `python-check-comint-prompt' returns nil."
  (python-send-string string)
  (let ((proc (python-proc)))
    (with-current-buffer (process-buffer proc)
      (when (python-check-comint-prompt proc)
	(set (make-local-variable 'python-preoutput-result) nil)
	(while (progn
		 (accept-process-output proc 5)
		 (null python-preoutput-result)))
	(prog1 python-preoutput-result
	  (kill-local-variable 'python-preoutput-result))))))

(defun python-check-comint-prompt (&optional proc)
  "Return non-nil if and only if there's a normal prompt in the inferior buffer.
If there isn't, it's probably not appropriate to send input to return Eldoc
information etc.  If PROC is non-nil, check the buffer for that process."
  (with-current-buffer (process-buffer (or proc (python-proc)))
    (save-excursion
      (save-match-data
	(re-search-backward (concat python--prompt-regexp " *\\=")
			    nil t)))))

;; Fixme:  Is there anything reasonable we can do with random methods?
;; (Currently only works with functions.)
(defun python-eldoc-function ()
  "`eldoc-documentation-function' for Python.
Only works when point is in a function name, not its arg list, for
instance.  Assumes an inferior Python is running."
  (let ((symbol (with-syntax-table python-dotty-syntax-table
		  (current-word))))
    ;; This is run from timers, so inhibit-quit tends to be set.
    (with-local-quit
      ;; First try the symbol we're on.
      (or (and symbol
	       (python-send-receive (format "emacs.eargs(%S, %s)"
					    symbol python-imports)))
	  ;; Try moving to symbol before enclosing parens.
	  (let ((s (syntax-ppss)))
	    (unless (zerop (car s))
	      (when (eq ?\( (char-after (nth 1 s)))
		(save-excursion
		  (goto-char (nth 1 s))
		  (skip-syntax-backward "-")
		  (let ((point (point)))
		    (skip-chars-backward "a-zA-Z._")
		    (if (< (point) point)
			(python-send-receive
			 (format "emacs.eargs(%S, %s)"
				 (buffer-substring-no-properties (point) point)
				 python-imports))))))))))))

;;;; Info-look functionality.

(declare-function info-lookup-maybe-add-help "info-look" (&rest arg))

;;;###autoload
(defun python-after-info-look ()
  "Set up info-look for Python.
Used with `eval-after-load'."
  (let* ((version (let ((s (shell-command-to-string (concat python-command
							    " -V"))))
		    (string-match "^Python \\([0-9]+\\.[0-9]+\\>\\)" s)
		    (match-string 1 s)))
	 ;; Whether info files have a Python version suffix, e.g. in Debian.
	 (versioned
	  (with-temp-buffer
	    (with-no-warnings (Info-mode))
	    (condition-case ()
		;; Don't use `info' because it would pop-up a *info* buffer.
		(with-no-warnings
		  (Info-goto-node (format "(python%s-lib)Miscellaneous Index"
					  version))
		  t)
	      (error nil)))))
    (info-lookup-maybe-add-help
     :mode 'python-mode
     :regexp "[[:alnum:]_]+"
     :doc-spec
     ;; Fixme: Can this reasonably be made specific to indices with
     ;; different rules?  Is the order of indices optimal?
     ;; (Miscellaneous in -ref first prefers lookup of keywords, for
     ;; instance.)
     (if versioned
	 ;; The empty prefix just gets us highlighted terms.
	 `((,(concat "(python" version "-ref)Miscellaneous Index") nil "")
	   (,(concat "(python" version "-ref)Module Index" nil ""))
	   (,(concat "(python" version "-ref)Function-Method-Variable Index"
		     nil ""))
	   (,(concat "(python" version "-ref)Class-Exception-Object Index"
		     nil ""))
	   (,(concat "(python" version "-lib)Module Index" nil ""))
	   (,(concat "(python" version "-lib)Class-Exception-Object Index"
		     nil ""))
	   (,(concat "(python" version "-lib)Function-Method-Variable Index"
		     nil ""))
	   (,(concat "(python" version "-lib)Miscellaneous Index" nil "")))
       '(("(python-ref)Miscellaneous Index" nil "")
	 ("(python-ref)Module Index" nil "")
	 ("(python-ref)Function-Method-Variable Index" nil "")
	 ("(python-ref)Class-Exception-Object Index" nil "")
	 ("(python-lib)Module Index" nil "")
	 ("(python-lib)Class-Exception-Object Index" nil "")
	 ("(python-lib)Function-Method-Variable Index" nil "")
	 ("(python-lib)Miscellaneous Index" nil ""))))))
(eval-after-load "info-look" '(python-after-info-look))

;;;; Miscellany.

(defcustom python-jython-packages '("java" "javax" "org" "com")
  "Packages implying `jython-mode'.
If these are imported near the beginning of the buffer, `python-mode'
actually punts to `jython-mode'."
  :type '(repeat string)
  :group 'python)

;; Called from `python-mode', this causes a recursive call of the
;; mode.  See logic there to break out of the recursion.
(defun python-maybe-jython ()
  "Invoke `jython-mode' if the buffer appears to contain Jython code.
The criterion is either a match for `jython-mode' via
`interpreter-mode-alist' or an import of a module from the list
`python-jython-packages'."
  ;; The logic is taken from python-mode.el.
  (save-excursion
    (save-restriction
      (widen)
      (goto-char (point-min))
      (let ((interpreter (if (looking-at auto-mode-interpreter-regexp)
			     (match-string 2))))
	(if (and interpreter (eq 'jython-mode
				 (cdr (assoc (file-name-nondirectory
					      interpreter)
					     interpreter-mode-alist))))
	    (jython-mode)
	  (if (catch 'done
		(while (re-search-forward
			(rx line-start (or "import" "from") (1+ space)
			    (group (1+ (not (any " \t\n.")))))
			(+ (point-min) 10000) ; Probably not worth customizing.
			t)
		  (if (member (match-string 1) python-jython-packages)
		      (throw 'done t))))
	      (jython-mode)))))))

(defun python-fill-paragraph (&optional justify)
  "`fill-paragraph-function' handling multi-line strings and possibly comments.
If any of the current line is in or at the end of a multi-line string,
fill the string or the paragraph of it that point is in, preserving
the string's indentation."
  (interactive "P")
  (or (fill-comment-paragraph justify)
      (save-excursion
	(end-of-line)
	(let* ((syntax (syntax-ppss))
	       (orig (point))
	       start end)
	  (cond ((nth 4 syntax)	; comment.   fixme: loses with trailing one
		 (let (fill-paragraph-function)
		   (fill-paragraph justify)))
		;; The `paragraph-start' and `paragraph-separate'
		;; variables don't allow us to delimit the last
		;; paragraph in a multi-line string properly, so narrow
		;; to the string and then fill around (the end of) the
		;; current line.
		((eq t (nth 3 syntax))	; in fenced string
		 (goto-char (nth 8 syntax)) ; string start
		 (setq start (line-beginning-position))
		 (setq end (condition-case () ; for unbalanced quotes
                               (progn (forward-sexp)
                                      (- (point) 3))
                             (error (point-max)))))
		((re-search-backward "\\s|\\s-*\\=" nil t) ; end of fenced string
		 (forward-char)
		 (setq end (point))
		 (condition-case ()
		     (progn (backward-sexp)
			    (setq start (line-beginning-position)))
		   (error nil))))
	  (when end
	    (save-restriction
	      (narrow-to-region start end)
	      (goto-char orig)
	      ;; Avoid losing leading and trailing newlines in doc
	      ;; strings written like:
	      ;;   """
	      ;;   ...
	      ;;   """
	      (let ((paragraph-separate
		     ;; Note that the string could be part of an
		     ;; expression, so it can have preceding and
		     ;; trailing non-whitespace.
		     (concat
		      (rx (or
			   ;; Opening triple quote without following text.
			   (and (* nonl)
				(group (syntax string-delimiter))
				(repeat 2 (backref 1))
				;; Fixme:  Not sure about including
				;; trailing whitespace.
				(* (any " \t"))
				eol)
			   ;; Closing trailing quote without preceding text.
			   (and (group (any ?\" ?')) (backref 2)
				(syntax string-delimiter))))
		      "\\(?:" paragraph-separate "\\)"))
		    fill-paragraph-function)
		(fill-paragraph justify))))))) t)

(defun python-shift-left (start end &optional count)
  "Shift lines in region COUNT (the prefix arg) columns to the left.
COUNT defaults to `python-indent'.  If region isn't active, just shift
current line.  The region shifted includes the lines in which START and
END lie.  It is an error if any lines in the region are indented less than
COUNT columns."
  (interactive
   (if mark-active
       (list (region-beginning) (region-end) current-prefix-arg)
     (list (line-beginning-position) (line-end-position) current-prefix-arg)))
  (if count
      (setq count (prefix-numeric-value count))
    (setq count python-indent))
  (when (> count 0)
    (save-excursion
      (goto-char start)
      (while (< (point) end)
	(if (and (< (current-indentation) count)
		 (not (looking-at "[ \t]*$")))
	    (error "Can't shift all lines enough"))
	(forward-line))
      (indent-rigidly start end (- count)))))

(add-to-list 'debug-ignored-errors "^Can't shift all lines enough")

(defun python-shift-right (start end &optional count)
  "Shift lines in region COUNT (the prefix arg) columns to the right.
COUNT defaults to `python-indent'.  If region isn't active, just shift
current line.  The region shifted includes the lines in which START and
END lie."
  (interactive
   (if mark-active
       (list (region-beginning) (region-end) current-prefix-arg)
     (list (line-beginning-position) (line-end-position) current-prefix-arg)))
  (if count
      (setq count (prefix-numeric-value count))
    (setq count python-indent))
  (indent-rigidly start end count))

(defun python-outline-level ()
  "`outline-level' function for Python mode.
The level is the number of `python-indent' steps of indentation
of current line."
  (1+ (/ (current-indentation) python-indent)))

;; Fixme: Consider top-level assignments, imports, &c.
(defun python-current-defun (&optional length-limit)
  "`add-log-current-defun-function' for Python."
  (save-excursion
    ;; Move up the tree of nested `class' and `def' blocks until we
    ;; get to zero indentation, accumulating the defined names.
    (let ((accum)
	  (length -1))
      (catch 'done
	(while (or (null length-limit)
		   (null (cdr accum))
		   (< length length-limit))
	  (let ((started-from (point)))
	    (python-beginning-of-block)
	    (end-of-line)
	    (beginning-of-defun)
	    (when (= (point) started-from)
	      (throw 'done nil)))
	  (when (looking-at (rx (0+ space) (or "def" "class") (1+ space)
				(group (1+ (or word (syntax symbol))))))
	    (push (match-string 1) accum)
	    (setq length (+ length 1 (length (car accum)))))
	  (when (= (current-indentation) 0)
	    (throw 'done nil))))
      (when accum
	(when (and length-limit (> length length-limit))
	  (setcar accum ".."))
	(mapconcat 'identity accum ".")))))

(defun python-mark-block ()
  "Mark the block around point.
Uses `python-beginning-of-block', `python-end-of-block'."
  (interactive)
  (push-mark)
  (python-beginning-of-block)
  (push-mark (point) nil t)
  (python-end-of-block)
  (exchange-point-and-mark))

;; Fixme:  Provide a find-function-like command to find source of a
;; definition (separate from BicycleRepairMan).  Complicated by
;; finding the right qualified name.

;;;; Completion.

;; http://lists.gnu.org/archive/html/bug-gnu-emacs/2008-01/msg00076.html
(defvar python-imports "None"
  "String of top-level import statements updated by `python-find-imports'.")
(make-variable-buffer-local 'python-imports)

;; Fixme: Should font-lock try to run this when it deals with an import?
;; Maybe not a good idea if it gets run multiple times when the
;; statement is being edited, and is more likely to end up with
;; something syntactically incorrect.
;; However, what we should do is to trundle up the block tree from point
;; to extract imports that appear to be in scope, and add those.
(defun python-find-imports ()
  "Find top-level imports, updating `python-imports'."
  (interactive)
  (save-excursion
      (let (lines)
	(goto-char (point-min))
	(while (re-search-forward "^import\\>\\|^from\\>" nil t)
	  (unless (syntax-ppss-context (syntax-ppss))
	    (let ((start (line-beginning-position)))
	      ;; Skip over continued lines.
	      (while (and (eq ?\\ (char-before (line-end-position)))
			  (= 0 (forward-line 1)))
		t)
	      (push (buffer-substring start (line-beginning-position 2))
		    lines))))
	(setq python-imports
	      (if lines
		  (apply #'concat
;; This is probably best left out since you're unlikely to need the
;; doc for a function in the buffer and the import will lose if the
;; Python sub-process' working directory isn't the same as the
;; buffer's.
;; 			 (if buffer-file-name
;; 			     (concat
;; 			      "import "
;; 			      (file-name-sans-extension
;; 			       (file-name-nondirectory buffer-file-name))))
			 (nreverse lines))
		"None"))
	(when lines
	  (set-text-properties 0 (length python-imports) nil python-imports)
	  ;; The output ends up in the wrong place if the string we
	  ;; send contains newlines (from the imports).
	  (setq python-imports
		(replace-regexp-in-string "\n" "\\n"
					  (format "%S" python-imports) t t))))))

;; Fixme: This fails the first time if the sub-process isn't already
;; running.  Presumably a timing issue with i/o to the process.
(defun python-symbol-completions (symbol)
  "Return a list of completions of the string SYMBOL from Python process.
The list is sorted.
Uses `python-imports' to load modules against which to complete."
  (when (stringp symbol)
    (let ((completions
	   (condition-case ()
	       (car (read-from-string
		     (python-send-receive
		      (format "emacs.complete(%S,%s)"
			      (substring-no-properties symbol)
			      python-imports))))
	     (error nil))))
      (sort
       ;; We can get duplicates from the above -- don't know why.
       (delete-dups completions)
       #'string<))))

(defun python-completion-at-point ()
  (let ((end (point))
	(start (save-excursion
		 (and (re-search-backward
		       (rx (or buffer-start (regexp "[^[:alnum:]._]"))
			   (group (1+ (regexp "[[:alnum:]._]"))) point)
		       nil t)
		      (match-beginning 1)))))
    (when start
      (list start end
            (completion-table-dynamic 'python-symbol-completions)))))

;;;; FFAP support

(defun python-module-path (module)
  "Function for `ffap-alist' to return path to MODULE."
  (python-send-receive (format "emacs.modpath (%S)" module)))

(eval-after-load "ffap"
  '(push '(python-mode . python-module-path) ffap-alist))

;;;; Find-function support

;; Fixme: key binding?

(defun python-find-function (name)
  "Find source of definition of function NAME.
Interactively, prompt for name."
  (interactive
   (let ((symbol (with-syntax-table python-dotty-syntax-table
		   (current-word)))
	 (enable-recursive-minibuffers t))
     (list (read-string (if symbol
			    (format "Find location of (default %s): " symbol)
			  "Find location of: ")
			nil nil symbol))))
  (unless python-imports
    (error "Not called from buffer visiting Python file"))
  (let* ((loc (python-send-receive (format "emacs.location_of (%S, %s)"
					   name python-imports)))
	 (loc (car (read-from-string loc)))
	 (file (car loc))
	 (line (cdr loc)))
    (unless file (error "Don't know where `%s' is defined" name))
    (pop-to-buffer (find-file-noselect file))
    (when (integerp line)
      (goto-char (point-min))
      (forward-line (1- line)))))

;;;; Skeletons

(defcustom python-use-skeletons nil
  "Non-nil means template skeletons will be automagically inserted.
This happens when pressing \"if<SPACE>\", for example, to prompt for
the if condition."
  :type 'boolean
  :group 'python)

(define-abbrev-table 'python-mode-abbrev-table ()
  "Abbrev table for Python mode."
  :case-fixed t
  ;; Allow / inside abbrevs.
  :regexp "\\(?:^\\|[^/]\\)\\<\\([[:word:]/]+\\)\\W*"
  ;; Only expand in code.
  :enable-function (lambda () (not (python-in-string/comment))))

(eval-when-compile
  ;; Define a user-level skeleton and add it to the abbrev table.
(defmacro def-python-skeleton (name &rest elements)
  (declare (indent 2))
  (let* ((name (symbol-name name))
	 (function (intern (concat "python-insert-" name))))
    `(progn
       ;; Usual technique for inserting a skeleton, but expand
       ;; to the original abbrev instead if in a comment or string.
       (when python-use-skeletons
         (define-abbrev python-mode-abbrev-table ,name ""
           ',function
           nil t))                      ; system abbrev
       (define-skeleton ,function
	 ,(format "Insert Python \"%s\" template." name)
	 ,@elements)))))

;; From `skeleton-further-elements' set below:
;;  `<': outdent a level;
;;  `^': delete indentation on current line and also previous newline.
;;       Not quite like `delete-indentation'.  Assumes point is at
;;       beginning of indentation.

(def-python-skeleton if
  "Condition: "
  "if " str ":" \n
  > -1	   ; Fixme: I don't understand the spurious space this removes.
  _ \n
  ("other condition, %s: "
   <			; Avoid wrong indentation after block opening.
   "elif " str ":" \n
   > _ \n nil)
  '(python-else) | ^)

(define-skeleton python-else
  "Auxiliary skeleton."
  nil
  (unless (eq ?y (read-char "Add `else' clause? (y for yes or RET for no) "))
    (signal 'quit t))
  < "else:" \n
  > _ \n)

(def-python-skeleton while
  "Condition: "
  "while " str ":" \n
  > -1 _ \n
  '(python-else) | ^)

(def-python-skeleton for
  "Target, %s: "
  "for " str " in " (skeleton-read "Expression, %s: ") ":" \n
  > -1 _ \n
  '(python-else) | ^)

(def-python-skeleton try/except
  nil
  "try:" \n
  > -1 _ \n
  ("Exception, %s: "
   < "except " str '(python-target) ":" \n
   > _ \n nil)
  < "except:" \n
  > _ \n
  '(python-else) | ^)

(define-skeleton python-target
  "Auxiliary skeleton."
  "Target, %s: " ", " str | -2)

(def-python-skeleton try/finally
  nil
  "try:" \n
  > -1 _ \n
  < "finally:" \n
  > _ \n)

(def-python-skeleton def
  "Name: "
  "def " str " (" ("Parameter, %s: " (unless (equal ?\( (char-before)) ", ")
		     str) "):" \n
  "\"\"\"" - "\"\"\"" \n     ; Fixme:  extra space inserted -- why?).
  > _ \n)

(def-python-skeleton class
  "Name: "
  "class " str " (" ("Inheritance, %s: "
		     (unless (equal ?\( (char-before)) ", ")
		     str)
  & ")" | -2				; close list or remove opening
  ":" \n
  "\"\"\"" - "\"\"\"" \n
  > _ \n)

(defvar python-default-template "if"
  "Default template to expand by `python-expand-template'.
Updated on each expansion.")

(defun python-expand-template (name)
  "Expand template named NAME.
Interactively, prompt for the name with completion."
  (interactive
   (list (completing-read (format "Template to expand (default %s): "
				  python-default-template)
			  python-mode-abbrev-table nil t nil nil
                          python-default-template)))
  (if (equal "" name)
      (setq name python-default-template)
    (setq python-default-template name))
  (let ((sym (abbrev-symbol name python-mode-abbrev-table)))
    (if sym
        (abbrev-insert sym)
      (error "Undefined template: %s" name))))

;;;; Bicycle Repair Man support

(autoload 'pymacs-load "pymacs" nil t)
(autoload 'brm-init "bikeemacs")
(defvar brm-menu)

;; I'm not sure how useful BRM really is, and it's certainly dangerous
;; the way it modifies files outside Emacs...  Also note that the
;; current BRM loses with tabs used for indentation -- I submitted a
;; fix <URL:http://www.loveshack.ukfsn.org/emacs/bikeemacs.py.diff>.
(defun python-setup-brm ()
  "Set up Bicycle Repair Man refactoring tool (if available).

Note that the `refactoring' features change files independently of
Emacs and may modify and save the contents of the current buffer
without confirmation."
  (interactive)
  (condition-case data
      (unless (fboundp 'brm-rename)
	(pymacs-load "bikeemacs" "brm-") ; first line of normal recipe
	(let ((py-mode-map (make-sparse-keymap)) ; it assumes this
	      (features (cons 'python-mode features))) ; and requires this
	  (brm-init)			; second line of normal recipe
	  (remove-hook 'python-mode-hook ; undo this from `brm-init'
		       (lambda () (easy-menu-add brm-menu)))
	  (easy-menu-define
	    python-brm-menu python-mode-map
	    "Bicycle Repair Man"
	    '("BicycleRepairMan"
	      :help "Interface to navigation and refactoring tool"
	      "Queries"
	      ["Find References" brm-find-references
	       :help "Find references to name at point in compilation buffer"]
	      ["Find Definition" brm-find-definition
	       :help "Find definition of name at point"]
	      "-"
	      "Refactoring"
	      ["Rename" brm-rename
	       :help "Replace name at point with a new name everywhere"]
	      ["Extract Method" brm-extract-method
	       :active (and mark-active (not buffer-read-only))
	       :help "Replace statements in region with a method"]
	      ["Extract Local Variable" brm-extract-local-variable
	       :active (and mark-active (not buffer-read-only))
	       :help "Replace expression in region with an assignment"]
	      ["Inline Local Variable" brm-inline-local-variable
	       :help
	       "Substitute uses of variable at point with its definition"]
	      ;; Fixme:  Should check for anything to revert.
	      ["Undo Last Refactoring" brm-undo :help ""]))))
    (error (error "BicycleRepairMan setup failed: %s" data))))

;;;; Modes.

;; pdb tracking is alert once this file is loaded, but takes no action if
;; `python-pdbtrack-do-tracking-p' is nil.
(add-hook 'comint-output-filter-functions 'python-pdbtrack-track-stack-file)

(defvar outline-heading-end-regexp)
(defvar eldoc-documentation-function)
(defvar python-mode-running)            ;Dynamically scoped var.

;;;###autoload
(define-derived-mode python-mode prog-mode "Python"
  "Major mode for editing Python files.
Turns on Font Lock mode unconditionally since it is currently required
for correct parsing of the source.
See also `jython-mode', which is actually invoked if the buffer appears to
contain Jython code.  See also `run-python' and associated Python mode
commands for running Python under Emacs.

The Emacs commands which work with `defun's, e.g. \\[beginning-of-defun], deal
with nested `def' and `class' blocks.  They take the innermost one as
current without distinguishing method and class definitions.  Used multiple
times, they move over others at the same indentation level until they reach
the end of definitions at that level, when they move up a level.
\\<python-mode-map>
Colon is electric: it outdents the line if appropriate, e.g. for
an else statement.  \\[python-backspace] at the beginning of an indented statement
deletes a level of indentation to close the current block; otherwise it
deletes a character backward.  TAB indents the current line relative to
the preceding code.  Successive TABs, with no intervening command, cycle
through the possibilities for indentation on the basis of enclosing blocks.

\\[fill-paragraph] fills comments and multi-line strings appropriately, but has no
effect outside them.

Supports Eldoc mode (only for functions, using a Python process),
Info-Look and Imenu.  In Outline minor mode, `class' and `def'
lines count as headers.  Symbol completion is available in the
same way as in the Python shell using the `rlcompleter' module
and this is added to the Hippie Expand functions locally if
Hippie Expand mode is turned on.  Completion of symbols of the
form x.y only works if the components are literal
module/attribute names, not variables.  An abbrev table is set up
with skeleton expansions for compound statement templates.

\\{python-mode-map}"
  :group 'python
  (set (make-local-variable 'font-lock-defaults)
       '(python-font-lock-keywords nil nil nil nil
         ;; This probably isn't worth it.
         ;; (font-lock-syntactic-face-function
         ;;  . python-font-lock-syntactic-face-function)
         ))
  (set (make-local-variable 'syntax-propertize-function)
       python-syntax-propertize-function)
  (set (make-local-variable 'parse-sexp-lookup-properties) t)
  (set (make-local-variable 'parse-sexp-ignore-comments) t)
  (set (make-local-variable 'comment-start) "# ")
  (set (make-local-variable 'indent-line-function) #'python-indent-line)
  (set (make-local-variable 'indent-region-function) #'python-indent-region)
  (set (make-local-variable 'paragraph-start) "\\s-*$")
  (set (make-local-variable 'fill-paragraph-function) 'python-fill-paragraph)
  (set (make-local-variable 'require-final-newline) mode-require-final-newline)
  (set (make-local-variable 'add-log-current-defun-function)
       #'python-current-defun)
  (set (make-local-variable 'outline-regexp)
       (rx (* space) (or "class" "def" "elif" "else" "except" "finally"
			 "for" "if" "try" "while" "with")
	   symbol-end))
  (set (make-local-variable 'outline-heading-end-regexp) ":\\s-*\n")
  (set (make-local-variable 'outline-level) #'python-outline-level)
  (set (make-local-variable 'open-paren-in-column-0-is-defun-start) nil)
  (set (make-local-variable 'beginning-of-defun-function)
       'python-beginning-of-defun)
  (set (make-local-variable 'end-of-defun-function) 'python-end-of-defun)
  (add-hook 'which-func-functions 'python-which-func nil t)
  (setq imenu-create-index-function #'python-imenu-create-index)
  (set (make-local-variable 'eldoc-documentation-function)
       #'python-eldoc-function)
  (add-hook 'eldoc-mode-hook
	    (lambda () (run-python nil t)) ; need it running
	    nil t)
  (add-hook 'completion-at-point-functions
            'python-completion-at-point nil 'local)
  ;; Fixme: should be in hideshow.  This seems to be of limited use
  ;; since it isn't (can't be) indentation-based.  Also hide-level
  ;; doesn't seem to work properly.
  (add-to-list 'hs-special-modes-alist
	       `(python-mode "^\\s-*\\(?:def\\|class\\)\\>" nil "#"
		 ,(lambda (_arg)
		    (python-end-of-defun)
		    (skip-chars-backward " \t\n"))
		 nil))
  (set (make-local-variable 'skeleton-further-elements)
       '((< '(backward-delete-char-untabify (min python-indent
						 (current-column))))
	 (^ '(- (1+ (current-indentation))))))
  ;; Python defines TABs as being 8-char wide.
  (set (make-local-variable 'tab-width) 8)
  (when python-guess-indent (python-guess-indent))
  ;; Let's make it harder for the user to shoot himself in the foot.
  (unless (= tab-width python-indent)
    (setq indent-tabs-mode nil))
  (set (make-local-variable 'python-command) python-python-command)
  (python-find-imports)
  (unless (boundp 'python-mode-running)	; kill the recursion from jython-mode
    (let ((python-mode-running t))
      (python-maybe-jython))))

;; Not done automatically in Emacs 21 or 22.
(defcustom python-mode-hook nil
  "Hook run when entering Python mode."
  :group 'python
  :type 'hook)
(custom-add-option 'python-mode-hook 'imenu-add-menubar-index)
(custom-add-option 'python-mode-hook
		   (lambda ()
		     "Turn off Indent Tabs mode."
		     (setq indent-tabs-mode nil)))
(custom-add-option 'python-mode-hook 'turn-on-eldoc-mode)
(custom-add-option 'python-mode-hook 'abbrev-mode)
(custom-add-option 'python-mode-hook 'python-setup-brm)

;;;###autoload
(define-derived-mode jython-mode python-mode  "Jython"
  "Major mode for editing Jython files.
Like `python-mode', but sets up parameters for Jython subprocesses.
Runs `jython-mode-hook' after `python-mode-hook'."
  :group 'python
  (set (make-local-variable 'python-command) python-jython-command))



;; pdbtrack features

(defun python-pdbtrack-overlay-arrow (activation)
  "Activate or deactivate arrow at beginning-of-line in current buffer."
  (if activation
      (progn
        (setq overlay-arrow-position (make-marker)
              overlay-arrow-string "=>"
              python-pdbtrack-is-tracking-p t)
        (set-marker overlay-arrow-position
                    (line-beginning-position)
                    (current-buffer)))
    (setq overlay-arrow-position nil
          python-pdbtrack-is-tracking-p nil)))

(defun python-pdbtrack-track-stack-file (_text)
  "Show the file indicated by the pdb stack entry line, in a separate window.

Activity is disabled if the buffer-local variable
`python-pdbtrack-do-tracking-p' is nil.

We depend on the pdb input prompt being a match for
`python-pdbtrack-input-prompt'.

If the traceback target file path is invalid, we look for the
most recently visited python-mode buffer which either has the
name of the current function or class, or which defines the
function or class.  This is to provide for scripts not in the
local file system (e.g., Zope's 'Script \(Python)', but it's not
Zope specific).  If you put a copy of the script in a buffer
named for the script and activate python-mode, then pdbtrack will
find it."
  ;; Instead of trying to piece things together from partial text
  ;; (which can be almost useless depending on Emacs version), we
  ;; monitor to the point where we have the next pdb prompt, and then
  ;; check all text from comint-last-input-end to process-mark.
  ;;
  ;; Also, we're very conservative about clearing the overlay arrow,
  ;; to minimize residue.  This means, for instance, that executing
  ;; other pdb commands wipe out the highlight.  You can always do a
  ;; 'where' (aka 'w') PDB command to reveal the overlay arrow.

  (let* ((origbuf (current-buffer))
	 (currproc (get-buffer-process origbuf)))

    (if (not (and currproc python-pdbtrack-do-tracking-p))
        (python-pdbtrack-overlay-arrow nil)

      (let* ((procmark (process-mark currproc))
             (block (buffer-substring (max comint-last-input-end
                                           (- procmark
                                              python-pdbtrack-track-range))
                                      procmark))
             target target_fname target_lineno target_buffer)

        (if (not (string-match (concat python-pdbtrack-input-prompt "$") block))
            (python-pdbtrack-overlay-arrow nil)

          (setq block (ansi-color-filter-apply block))
          (setq target (python-pdbtrack-get-source-buffer block))

          (if (stringp target)
              (progn
                (python-pdbtrack-overlay-arrow nil)
                (message "pdbtrack: %s" target))

            (setq target_lineno (car target)
                  target_buffer (cadr target)
                  target_fname (buffer-file-name target_buffer))
            (switch-to-buffer-other-window target_buffer)
            (goto-char (point-min))
            (forward-line (1- target_lineno))
            (message "pdbtrack: line %s, file %s" target_lineno target_fname)
            (python-pdbtrack-overlay-arrow t)
            (pop-to-buffer origbuf t)
            ;; in large shell buffers, above stuff may cause point to lag output
            (goto-char procmark)
            )))))
  )

(defun python-pdbtrack-get-source-buffer (block)
  "Return line number and buffer of code indicated by block's traceback text.

We look first to visit the file indicated in the trace.

Failing that, we look for the most recently visited python-mode buffer
with the same name or having the named function.

If we're unable find the source code we return a string describing the
problem."

  (if (not (string-match python-pdbtrack-stack-entry-regexp block))

      "Traceback cue not found"

    (let* ((filename (match-string 1 block))
           (lineno (string-to-number (match-string 2 block)))
           (funcname (match-string 3 block))
           funcbuffer)

      (cond ((file-exists-p filename)
             (list lineno (find-file-noselect filename)))

            ((setq funcbuffer (python-pdbtrack-grub-for-buffer funcname lineno))
             (if (string-match "/Script (Python)$" filename)
                 ;; Add in number of lines for leading '##' comments:
                 (setq lineno
                       (+ lineno
                          (with-current-buffer funcbuffer
                            (if (equal (point-min)(point-max))
                                0
                              (count-lines
                               (point-min)
                               (max (point-min)
                                    (string-match "^\\([^#]\\|#[^#]\\|#$\\)"
                                                  (buffer-substring
                                                   (point-min) (point-max)))
                                    )))))))
               (list lineno funcbuffer))

            ((= (elt filename 0) ?\<)
             (format "(Non-file source: '%s')" filename))

            (t (format "Not found: %s(), %s" funcname filename)))
      )
    )
  )

(defun python-pdbtrack-grub-for-buffer (funcname _lineno)
  "Find recent Python mode buffer named, or having function named FUNCNAME."
  (let ((buffers (buffer-list))
        buf
        got)
    (while (and buffers (not got))
      (setq buf (car buffers)
            buffers (cdr buffers))
      (if (and (with-current-buffer buf
                 (string= major-mode "python-mode"))
               (or (string-match funcname (buffer-name buf))
                   (string-match (concat "^\\s-*\\(def\\|class\\)\\s-+"
                                         funcname "\\s-*(")
                                 (with-current-buffer buf
                                   (buffer-substring (point-min)
                                                     (point-max))))))
          (setq got buf)))
    got))

;; Python subprocess utilities and filters
(defun python-execute-file (proc filename)
  "Send to Python interpreter process PROC \"execfile('FILENAME')\".
Make that process's buffer visible and force display.  Also make
comint believe the user typed this string so that
`kill-output-from-shell' does The Right Thing."
  (let ((curbuf (current-buffer))
	(procbuf (process-buffer proc))
;	(comint-scroll-to-bottom-on-output t)
	(msg (format "## working on region in file %s...\n" filename))
        ;; add some comment, so that we can filter it out of history
	(cmd (format "execfile(r'%s') # PYTHON-MODE\n" filename)))
    (unwind-protect
	(with-current-buffer procbuf
	  (goto-char (point-max))
	  (move-marker (process-mark proc) (point))
	  (funcall (process-filter proc) proc msg))
      (set-buffer curbuf))
    (process-send-string proc cmd)))

(defun python-pdbtrack-toggle-stack-tracking (arg)
  (interactive "P")
  (if (not (get-buffer-process (current-buffer)))
      (error "No process associated with buffer '%s'" (current-buffer)))
  ;; missing or 0 is toggle, >0 turn on, <0 turn off
  (if (or (not arg)
	  (zerop (setq arg (prefix-numeric-value arg))))
      (setq python-pdbtrack-do-tracking-p (not python-pdbtrack-do-tracking-p))
    (setq python-pdbtrack-do-tracking-p (> arg 0)))
  (message "%sabled Python's pdbtrack"
           (if python-pdbtrack-do-tracking-p "En" "Dis")))

(defun turn-on-pdbtrack ()
  (interactive)
  (python-pdbtrack-toggle-stack-tracking 1))

(defun turn-off-pdbtrack ()
  (interactive)
  (python-pdbtrack-toggle-stack-tracking 0))

(defun python-sentinel (_proc _msg)
  (setq overlay-arrow-position nil))

(defun python-unload-function ()
  "Unload the Python library."
  (remove-hook 'comint-output-filter-functions 'python-pdbtrack-track-stack-file)
  (setq minor-mode-alist (assq-delete-all 'python-pdbtrack-is-tracking-p
                                          minor-mode-alist))
  (dolist (error '("^No symbol" "^Can't shift all lines enough"))
    (setq debug-ignored-errors (delete error debug-ignored-errors)))
  ;; continue standard unloading
  nil)

(provide 'python)
(provide 'python-21)

;;; python.el ends here