[python-win32] regarding invoking command prompt using python
Philip Bloom
pbloom at crystald.com
Thu Jun 18 00:29:54 CEST 2009
That logic seems weird to me.
This is why it feels weird:
The cmd shell itself is a running application that only changes its own
environment parameters. This is no different from the limitation that
Python's os.putenv has, as it only affects the Cmd process and children
of that process. It does not affect other cmd processes that may be
running or the real global environment. The SET command (and batch
scripts) are simply sending commands that are executed by that
application. "Python.exe" as a lower level process does not standardly
change the runtime environment of a higher level one (And if that's
doable at all, it's done by asking the OS to do, not actually done by
the process itself).
Maybe I'm misunderstanding what's being asked, but cmd doesn't do any
special magic that changes the rules as far as a shell. If you leave
the shell to a higher level environment, you do not have what you set up
in the shell. Equally, while you can change the defaults, it does not
adjust running processes, since that'd likely break the environment of
running processes.
________________________________
From: python-win32-bounces+pbloom=crystald.com at python.org
[mailto:python-win32-bounces+pbloom=crystald.com at python.org] On Behalf
Of Vernon Cole
Sent: Wednesday, June 17, 2009 1:54 PM
To: Python-Win32 List
Subject: Re: [python-win32] regarding invoking command prompt using
python
Everyone:
If I read the request correctly, this question is about how to set
environment variables from a python script.
In other words: what is the Python equivalent of the DOS command:
SET envrmnt="This is the new value"
If my experience is correct (I would love it if someone will tell me
that I am wrong) it cannot be done.
There are two modules which look like they should work, but they only
affect processes which are children of the python code, not the
environment from which it is running. (See the console trace below)
<begin cmd console dump>
C:>c:\python26\python.exe
Python 2.6.2 (r262:71605, Apr 14 2009, 22:40:02) [MSC v.1500 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.putenv('x','xxx')
>>> os.system('set x') # run a child process
x=xxx
0
>>> print repr(os.getenv('x'))
None
>>>exit()
C:>set x="zzz"
C:>c:\python26\python.exe
Python 2.6.2 (r262:71605, Apr 14 2009, 22:40:02) [MSC v.1500 32 bit
(Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import win32api
>>> win32api.SetEnvironmentVariable('X','xxx')
>>> import os
>>> print repr(os.getenv('X'))
'zzz'
>>>
<end console dump>
There MUST be some api to actually do what a SET command does, otherwise
the CMD shell itself could not do it, but I have never seen any
documentation for it. This seem to me to be the only thing which keeps
one from running Python as a command shell.
------------------------------------------------------------------------
-------------------------
Dear a h:
The only way I know to permanently set environment variables is:
-Right-click on "My Computer"
-select "Properties"
-select "Advanced System Settings"
-click on "Environment Variables"
Many of us old DOS hackers keep a directory of utility scripts to make
running command-line commands easier.
I am in the habit of creating a C:\utils folder and putting all of my
quick scripts in there. Then I go through the Windows steps (as above)
and edit my PATH environment variable to concatenate ";C:\utils" to the
end of whatever is already there.
Into the C:\utils folder I place a few handy filters, such as Tail.exe,
touch.exe, and less.exe. Mosly it contains a bunch of .bat files. For
example, ls.bat contains only one line of text, which is: "dir %1 %2 %3
%4 %5 %6 %7 %8 %9".
So when I forget which operating system I am using and type "ls *.txt",
it works.
More important are the Python helpers.
python.bat contains: "c:\python26\python.exe %1 %2 %3 %4 %5 %6 %7 %8 %9"
py30.bat contains: "c:\python30\python.exe %1 %2 %3 %4 %5 %6 %7 %8 %9"
ipy.bat contains: ""c:\program files\Ironpython 2.0.1\ipy.exe" %1 %2 %3
%4 %5 %6 %7 %8 %9"
ped.bat contains: "start
c:\python26\Lib\site-packages\pythonwin\pythonwin.exe %1 %2 %3"
2to3.bat contains: "c:\python26\python.exe
c:\python26\Tools\Scripts\2to3.py %1 %2 %3 %4 %5 %6 %7 %8 %9"
Suppose I am running a console cmd window in a directory which contains
the script "testme.py" and I want to test under different environments.
I type:
>python testme.py
>ipy testme.py
>copy testme.py testme3.py
>2to3 testme3.py --write
>py30 testme3.py
Hope this helps a little.
--
Vernon Cole
On Wed, Jun 17, 2009 at 12:54 PM, Tim Roberts <timr at probo.com> wrote:
a h wrote:
>
> thanks for the reply, what i have done to set up the
environment
> variables is open the command prompt and then has given the
whole path
> of c:\..\vsvars32.bat and then enter.
> A message appear is "setting environment for using MS visual
studio".
> and then using DEVENV i had build my solution.
"devenv" is a fairly heavyweight way to do that. It basically
invokes
the whole IDE. If you are using Visual Studio 2005 or 2008, you
can say
msbuild xxxx.sln
which is not quite so heavy as devenv. If you're using an older
Visual
Studio, that may not be available.
> can u please help me out that how do i perform above steps in
python.
> code snippet is required.
I was going to say "just write the commands out to a temporary
batch
file, then call os.system or subprocess.call to run the batch
file"
until I read this followup:
a h wrote:
>
> 1.I want to know how do i write batchfile kind of file in
python so
> that it executes some commands. Code snippets are required.
For the future, the way you worded that is impolite. When you
say
"required", it is as if you are demanding something from us. It
would
be better to say "Please provide code snippets."
> 2.As well how do i invoke command prompt.
>
> Actually what i need is that i have to perform certain things
in
> windows...first i have to go to start->run->type cmd
> then command prompt window is open... in that to run an .exe i
have to
> give the whole path like this c:\> cd
> temp_folder\next_folder\test.exe... and many more commands...
> So I want this to be perfomed in python. please help
Can't you just work this out for yourself? You create a file,
you write
to it, you run it:
fbat = open( "xxx.bat", "w" )
print >> fbat, "echo I'm inside a batch file"
print >> fbat, 'call "c:\\Program Files\\Microsoft
etc\\vsvars32.bat'"
print >> fbat, 'msbuild myproject.sln'
fbat.close()
os.system( "xxx.bat" )
os.remove( "xxx.bat" )
Note that you will need extra quotes when the path includes
spaces.
Note also the escaped backslash characters.
--
Tim Roberts, timr at probo.com
Providenza & Boekelheide, Inc.
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