[issue16633] os.environ updates only one copy of env vars under Windows (GetEnvironmentVariable vs. getenv)
Václav Šmilauer
report at bugs.python.org
Fri Dec 7 18:11:50 CET 2012
Václav Šmilauer added the comment:
I checked on Windows 7 64bit with python 2.7 (sorry, not python 3.3 installed here) with the script attached. Each line sets a variable using the method in the very left column, then it attempts to read it back using all methods.
os.environ win32 os.?etenv msvcrt msvcr?
os.environ OK OK OK -- --
win32 -- OK -- -- --
os.?etenv -- OK -- -- --
msvcrt -- OK -- OK --
msvcr? -- OK -- -- --
Methods which can read back what they also set are os.environ, win32api, msvcrt. OTOH, msvcr? (which is ctypes.util.find_msvcr(), in my case msvcr90.dll) does not read its own values, just like os.getenv/os.putenv.
It *seems* that reading with win32 API is very reliable (that is not a good news for writing cross-platform extension modules), though, but perhaps it just asks the CRT if it does not find the variable defined (my testing did not go that far).
@Andrew: you're probably right, though it does not explain, why msvcr90.dll does not read back the values I set in there - that is the CRT python27.dll itself links to --
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Added file: http://bugs.python.org/file28243/tryenv2.py
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