GNU bug report logs - #6782
python.el's run-python removes current directory from sys.path

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jim Blandy <jimb <at> red-bean.com>
To: bug-gnu-emacs <at> gnu.org
Subject: python.el's run-python removes current directory from sys.path
Date: Mon, 2 Aug 2010 11:11:48 -0700

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the emacs-pretest-bug <at> gnu.org mailing list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

Suppose I have a directory set up as follows:

  $ ls
  a.py  b.py
  $ cat a.py
  import b
  b.hello()
  $ cat b.py
  def hello():
      print "Hello!"

In most normal ways of running Python, a.py is able to find b.py, even
though PYTHONPATH is not set:

  $ python
  Python 2.6.4 (r264:75706, Dec  7 2009, 18:45:15)
  [GCC 4.4.1] on linux2
  Type "help", "copyright", "credits" or "license" for more information.
  >>> import a
  Hello!
  >>>
  $ python a.py
  Hello!
  $ echo $PYTHONPATH

  $

However, if I visit a.py in Emacs, and then hit `C-c C-c'
(python-send-buffer), I get the following error:

  >>> Traceback (most recent call last):
    File "/tmp/py6932ha1", line 1, in <module>
      import b
  ImportError: No module named b
  >>>

I think the problem is in the way Emacs' python-mode runs Python. If I
type M-x run-python, then I see this:

  >>> import sys
  >>> '' in sys.path
  False
  >>>

whereas if I run the python interpreter from the shell, I see:

  >>> import sys
  >>> '' in sys.path
  True
  >>>

This seems to be due to the following code in run-python from
progmodes/python.el:

  (let* ((cmdlist
      (append (python-args-to-list cmd)
          '("-i" "-c" "import sys; sys.path.remove('')")))

which has no comment, and the following helpful ChangeLog entry:

2008-08-24  Romain Francoise  <romain <at> orebokech.com>

        * progmodes/python.el (run-python): Remove '' from sys.path.

Here's a workaround that one can put in one's .emacs file:

(defun python-reinstate-current-directory ()
  "When running Python, add the current directory ('') to the head of sys.path.
For reasons unexplained, run-python passes arguments to the
interpreter that explicitly remove '' from sys.path. This means
that, for example, using `python-send-buffer' in a buffer
visiting a module's code will fail to find other modules in the
same directory.

Adding this function to `inferior-python-mode-hook' reinstates
the current directory in Python's search path."
  (python-send-string "sys.path[0:0] = ['']"))

(add-hook 'inferior-python-mode-hook 'python-reinstate-current-directory)


In GNU Emacs 23.0.91.2 (i686-pc-linux-gnu, GTK+ Version 2.14.4)
 of 2009-03-20 on frida
Windowing system distributor `The X.Org Foundation', version 11.0.10604000
configured using `configure  '--prefix=/home/jimb/emacs''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Inferior Python

Minor modes in effect:
  compilation-shell-minor-mode: t
  erc-list-mode: t
  erc-menu-mode: t
  erc-autojoin-mode: t
  erc-ring-mode: t
  erc-networks-mode: t
  erc-pcomplete-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-match-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-stamp-mode: t
  erc-netsplit-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
e s d <backspace> <backspace> <backspace> s e n d -
s t r i n g SPC " s y s . p a t h [ : 0 <backspace>
<backspace> : 0 <backspace> <backspace> 0 : 0 ] SPC
= SPC [ ' ' ] " C-b \ n <backspace> <backspace> C-e
C-a M-f M-f M-f C-e C-M-b C-M-f ) <return> <tab> (
C-a C-k C-M-b C-M-f M-> <backspace> ) <return> <return>
( a d d - h o o k SPC ' p y t h n <backspace> o n M-b
C-b C-h f <return> C-e M-b i n e f i o r <M-backspace>
i n f e r i o r - C-e / m o <backspace> <backspace>
<backspace> <M-tab> <M-tab> m <M-tab> - h <M-tab> C-h
f <return> SPC ' p y t h o n - i <backspace> r e i
M-/ ) C-j C-p C-k C-p C-p C-p C-p C-p C-M-x C-n C-n
C-n C-n C-e M-> <switch-frame> C-x b * <backspace>
* p <backspace> P t h <tab> <backspace> <backspace>
y t h <tab> <return> C-x k <return> M-x r u n - p y
t h <tab> <return> s y s . p a t h <return> C-x k <return>
M-x r u n - p y t h <tab> <return> s y s . p a t h
<return> C-x k <return> C-x b a . p <tab> <return>
C-c C-c C-x o C-x b * P T <backspace> y <tab> <return>
<help-echo> <switch-frame> <backspace> C-SPC C-p C-p
C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p M-w C-x
C-x C-4 C-x <tab> C-x C-x M-w <help-echo> <switch-frame>
<help-echo> M-x r e p o r t - e m a c s - b u g <r
eturn>

Recent messages:
Fontifying *Python*... (regexps...........)
Mark set
Making completion list...done
Type C-x 4 C-o RET to restore the other window.
python-reinstate-current-directory
Mark set
Fontifying *Python*... (regexps...........)
Fontifying *Python*... (regexps...........)
Fontifying *Python*... (regexps...........)
Mark set

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