Change %PATH% from Python Script (Windows)

Question

As part of a project, I need to ensure that a few paths are included in the user's %PATH% variable, which I am going to do at the beginning of the script. What's the best way to do this from a python script?

My first thought was to just use something like the following:

subprocess.call('path = %PATH%;c:\path1;c:\path2;c:\path3')

To add each of the paths, as this is how you would do it from the Windows command line, though my fear is that after a reboot these settings would not carry over (this is what seems to happen when I run it from the command line regularly - in order for it to stick, I actually have to go in through the GUI and change it).

Anyone have a better idea, or will this work as I'd like it to? (Ideally, the user will only have to execute this portion of the script once, at which point the 'setup' will be complete and not need to be run again)

Thanks!

User environment variables from HKCU\Environment get merged with system environment variables from HKLM\System\CurrentControlSet\Control\Session Manager\Environment. Append to whichever Path value is appropriate for your context. The data type is REG_EXPAND_SZ. Read the docs: docs.python.org/2/library/_winreg.html. — Eryk Sun
– Eryk Sun, Commented Mar 10, 2015 at 8:28

Community · Accepted Answer · 2017-05-23 12:23:07Z

-1

path = os.environ.get('PATH')
subprocess.call('setx /M PATH "' + path + ';c:\path1;c:\path2;c:\path3"')

...or use _winreg. Example from another question here: How to add to and remove from system's environment variable "PATH"?

edited May 23, 2017 at 12:23

CommunityBot

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answered Jan 4, 2016 at 22:33

fredrik

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2 Comments

Niko Fohr Over a year ago

This will mess your User Path since "PATH" contains both (union of User and System Path ) + setx has limitation of 1024 characters.

cowlinator Over a year ago

Yes, and on the average modern windows device, PATH is almost always longer than 1024

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