Set Windows Environment Variable
duncan.booth at invalid.invalid
Thu Mar 30 19:24:49 CEST 2006
> Magnus Lycka wrote:
>> Surely there must be a way to programatically set up the
>> environment variables for not yet started processes? I.e.
>> doing the same as when you manually change things in the
>> control panel. I'm pretty sure many Windows installers do
>> that, and while I suppose this is technically a registry
>> manipulation, I suspect there is a more direct API somewhere.
> I *believe* that ``SetEnvironmentVariable`` exists in the underlying
> windows API, but that it isn't wrapped by the win32api extension.
> I may be wrong.
No, there is a SetEnvironmentVariable call which sets environment variables
for the current process. From the documentation:
"This function has no effect on the system environment variables or the
environment variables of other processes."
I don't think it will have much effect on the currently running Python
process either since the you just access os.environ and that won't see
changes to the system's idea of the environment.
I took the original question as asking about already running processes. If
the question was about processes which have not yet been started then the
following may be of use:
"Calling SetEnvironmentVariable has no effect on the system environment
variables. The user can add or modify system environment variables using
the Control Panel. To programmatically add or modify system environment
variables, add them to the
Manager\Environment registry key, then broadcast a WM_SETTINGCHANGE
message. This allows applications, such as the shell, to pick up your
updates. Note that environment variables listed in this key are limited to
This would change the environment for any processes which respond to the
WM_SETTINGCHANGE message, and consequently any processes which they start.
Window's explorer will then update its environment so that future processes
that it starts will pick up the changes. I think that most other
applications, including window's CMD.EXE shell won't respond to this
message so you wouldn't see the changes in future processes they start.
See http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/55993 for how
to do this from Python.
More information about the Python-list