[Python-bugs-list] [ python-Bugs-463506 ] reload(os) fails for os.environ

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Bugs item #463506, was opened at 2001-09-21 03:05
You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=105470&aid=463506&group_id=5470

Category: Windows
Group: Python 2.1.1
Status: Closed
Resolution: Wont Fix
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Mark Hammond (mhammond)
Summary: reload(os) fails for os.environ

Initial Comment:


I used function KERNEL32::SetEnvironmentVariableA 
via Dynawrap.dll from
http://cwashington.netreach.net/main_site/
downloads/default.asp?topic=a-m
to add an new entry.

Then I tested the result with a scripting host 
component and the new entry was shown. But not working 
was this:

reload(os)
os.environ


PythonWin 2.1 (#15, Jun 18 2001, 21:42:28) [MSC 32 bit 
(Intel)] on win32.
Portions Copyright 1994-2001 Mark Hammond 
(MarkH@ActiveState.com) - see 'Help/About PythonWin' 
for further copyright information.
>>> import os
>>> os.environ
{'SNDSCAPE': 'C:\WINDOWS', 'CMDLINE': 'WIN', 'PATH': '
C:\PROGRAMME\PYTHON21
\;C:\WINDOWS;C:\WINDOWS\COMMAND', 'TEMP': 'C:\WIND
OWS\TEMP', 'COMSPEC': 'C:\WINDOWS\COMMAND.COM', 'PRO
MPT': '$p$g', 'WINBOOTDIR': 'C:\WINDOWS', 'WINDIR': 'C
:\WINDOWS', 'TMP': 'C:\WINDOWS\TEMP'}
>>> 
>>> from win32com.client import Dispatch
>>> dw = Dispatch("DynamicWrapper")
>>> dw.Register
("KERNEL32.DLL", "SetEnvironmentVariableA", "i=ss", "f=
s", "r=l")
1
>>> dw.SetEnvironmentVariableA
("MyNewEntry", "MyNewValue")
1
>>> reload(os)
<module 'os' from 'c:\programme\python21\lib\os.pyc'>
>>> os.environ
{'SNDSCAPE': 'C:\WINDOWS', 'CMDLINE': 'WIN', 'PATH': '
C:\PROGRAMME\PYTHON21
\;C:\WINDOWS;C:\WINDOWS\COMMAND', 'TEMP': 'C:\WIND
OWS\TEMP', 'COMSPEC': 'C:\WINDOWS\COMMAND.COM', 'PRO
MPT': '$p$g', 'WINBOOTDIR': 'C:\WINDOWS', 'WINDIR': 'C
:\WINDOWS', 'TMP': 'C:\WINDOWS\TEMP'}
>>> 
>>> sh = Dispatch("WScript.Shell")
>>> for string in sh.Environment._NewEnum():
... 	print string
... 	
TMP=C:\WINDOWS\TEMP
TEMP=C:\WINDOWS\TEMP
PROMPT=$p$g
winbootdir=C:\WINDOWS
COMSPEC=C:\WINDOWS\COMMAND.COM
PATH=C:\PROGRAMME\PYTHON21
\;C:\WINDOWS;C:\WINDOWS\COMMAND
CMDLINE=WIN
windir=C:\WINDOWS
SNDSCAPE=C:\WINDOWS
MYNEWENTRY=MyNewValue
>>> 


----------------------------------------------------------------------

>Comment By: Tim Peters (tim_one)
Date: 2001-09-21 17:29

Message:
Logged In: YES 
user_id=31435

Ah!  Good call.  WRT VC's putenv, the MS docs say:

"""
_putenv and _wputenv affect only the environment that is 
local to the current process; you cannot use them to modify 
the command-level environment. That is, these functions 
operate only on data structures accessible to the run-time 
library and not on the environment &#8220;segment&#8221; created for a 
process by the operating system. When the current process 
terminates, the environment reverts to the level of the 
calling process (in most cases, the operating-system 
level). However, the modified environment can be passed to 
any new processes created by _spawn, _exec, or system, and 
these new processes get any new items added by _putenv and 
_wputenv. 
"""

Sounds like the msvcrt-level env functions work with a copy 
of the process env block captured at process creation time.

As usual, a Bad Idea to try to use envars on Windows ...

----------------------------------------------------------------------

Comment By: Mark Hammond (mhammond)
Date: 2001-09-21 17:01

Message:
Logged In: YES 
user_id=14198

The complaint is that when the environment is set via the 
win32 API, os.environ appears to not pick up the new 
setting.

I have no idea why this is, but it is not Python's fault.  
Python uses the C runtime library, and there i snot much we 
can do about that.  I don't have time to try and locate the 
CRTL source code and figure out why either.  Marking 
as "Wont Fix"

----------------------------------------------------------------------

Comment By: Tim Peters (tim_one)
Date: 2001-09-21 14:47

Message:
Logged In: YES 
user_id=31435

Reassigned to MarkH.  I haven't figured out what the 
complaint is, but it looks like it has to do with the Win32 
extensions.

----------------------------------------------------------------------

Comment By: Nobody/Anonymous (nobody)
Date: 2001-09-21 05:00

Message:
Logged In: NO 

This is an altenative way to change the environment:

from win32com.client import Dispatch
sh = Dispatch("WScript.Shell")
sh.Environment['MYNEWENTRY'] = "bla-bla"
print sh.Environment['MYNEWENTRY']

----------------------------------------------------------------------

Comment By: Nobody/Anonymous (nobody)
Date: 2001-09-21 03:18

Message:
Logged In: NO 

Markus_Daniel@gmx.de

----------------------------------------------------------------------

Comment By: Nobody/Anonymous (nobody)
Date: 2001-09-21 03:08

Message:
Logged In: NO 

This Bug was submitted by Markus Daniel (Spacy73)

----------------------------------------------------------------------

You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=105470&aid=463506&group_id=5470