Add os.reload_environ() function

[vstinner]

Feature or enhancement

When the environment is modified outside Python, os.environ is not updated. I propose adding a new os.environ.refresh() method to manually update os.environ.

Discussion: https://discuss.python.org/t/method-to-refresh-os-environ/54774

Linked PRs

• gh-120057: Add os.environ.refresh() method #120059
• gh-120057: Add os.get_user_default_environ() function #120494
• Revert "gh-120057: Add os.environ.refresh() method (#120059)" #120789
• Revert "gh-120057: Add os.environ.refresh() method (#120059)" #120790
• gh-120057: Rename os.environ.refresh() to invalidate_cache() #120808
• gh-120057: Add os.reload_environ() function #126268
• gh-120057: add os.reload_environ to __all__ #140763
• [3.14] gh-120057: add os.reload_environ to __all__ (GH-140763) #140773

[eryksun]

Note that on Windows the C runtime's Unicode and multibyte environments -- _wenviron and _environ -- can get out of sync with the process environment -- GetEnvironmentStringsW() -- due to code that directly calls WinAPI SetEnvironmentVariableW(). It's possible to implement a function to fresh the C environment on Windows, which unsets the variables in _wenviron and sets the variables from GetEnvironmentStringsW(), but that's probably not something that the Python runtime needs to worry about.

[vstinner]

but that's probably not something that the Python runtime needs to worry about

As soon as there are different "caches", it's hard to keep everything in sync and consistent :-(

[erlend-aasland]

I'm not sure if this is a good idea. I suspect it will be a hard feature to get right, and as noted in the forum discussion, most beginners will misunderstand the feature.

[vstinner]

I suspect it will be a hard feature to get right

Would you mind to elaborate?

[vstinner]

and as noted in the forum discussion, most beginners will misunderstand the feature.

I added "in the same process" to reduce misunderstanding.

[picnixz]

FYI, there was this issue: #119737 (so you may want to close it to avoid duplicates)

[vstinner]

I closed issue #119737 as a duplicate of this issue.

[vstinner]

Implemented by the commit 7aff2de.