On Windows, subprocess.Popen requires the executable name and working directory to be ascii.  This is because it calls CreateProcess instead of CreateProcessW.

The docs say that args should be a string or sequence of strings. It also says "On Windows, the class uses the Windows CreateProcess() function.", so it is not a bug for it to do that. However, CreateProcessW sounds like a good (and overdue, and overlooked) enhancement, if it indeed is still not used in 3.4. (Have you checked?)

On 2.7, 'string' may or may not include unicode strings. On 3.x, it definitely does, and may or may not include bytes. If 3.x restricts unicode strings to ascii text (at least on Windows), the doc should say so.

I've checked the source code for 3.4; `subprocess` uses `_winapi.CreateProcess` on Windows [1] that in turn uses `CreateProcessW` [2]. CreateProcessA is not used.

`Popen` should already support Unicode on Windows though I don't see explicit tests for non-ascii arguments or arguments that can't be encoded using `mbcs` character encoding.

[1]: http://hg.python.org/cpython/file/3.4/Lib/subprocess.py#l1063
[2]: http://hg.python.org/cpython/file/3.4/Modules/_winapi.c#l579

Peter, can you post 1 or more failing examplex?  With some, I might be persuaded that this is a bug.

Victor, I know you have worked in this area. Any opinions?

I don't understand this issue. Python 3 uses CreateProcessW() and so
support the full Unicode range. I suggest to close this issue as invalid.

Popen() parameters are Unicode strings. It may support bytes string, but
passing bytes to OS functions on Windows is deprecated, especially for
filenames.

The issue is really that Terry had removed 2.7 from the list of affected versions, and added 3.4 instead. The original issue was reported against 2.7, where the observation that it uses CreateProcess is correct:

http://hg.python.org/cpython/file/babb9479b79f/PC/_subprocess.c#l463

The OP's observation that this restricts the supported executable names to be ascii is incorrect. Instead, any string in the CP_ACP ("ANSI") encoding of the system would work, which practically allows to access all directories on a typical installation.

I'd close this as "won't fix", except that I recall a recent discussion that lack of Unicode support in some API is considered a bug in 2.7.

So: patches welcome (not really - I wouldn't mind if this stays open until 2.7 is properly retired).

You're right, the bug/enhancement border for 2.7 unicode issues has been shifted a bit (or perhaps made a bit more consistent). A failing case is still needed.

>  The original issue was reported against 2.7

Oh... Ok :-)

It's tricky to fix this issue in Python 2.7 because you have to choose which function is used: CreateProcessA() (bytes) or CreateProcessW() (Unicode). To use CreateProcessW(), you have to decode bytes parameter. Python 3 has os.fsencode()/os.fsdecode() functions, similar functions in C. The "mbcs" Python codec is strict by default, but it now supports any Python error handler. This change changed was improved in each Python 3 release.

Python 2 has PyUnicode_DecodeMBCSStateful() and PyUnicode_EncodeMBCS() which use the default Windows behaviour. I'm not sure that using PyUnicode_DecodeMBCSStateful() (or directly MultiByteToWideChar) + CreateProcessW() is exactly the same than calling CreateProcessA().

Should we support CreateProcessA() and CreateProcessW(), and use one or the other depending on the type of the pararameters?

IMO such change requires too much work and it is not enough to have a full Unicode support for filenames. You have to fix much more code. I already did all this work in Python 3 (in 3.1, 3.2 and then 3.3). I suggest you to upgrade to port your application to Python 3 if you want a full Unicode support. Using Unicode in Python 3 is natural and just works fine.

So I still suggest to close this issue as wontfix.

--

Similar discussions on Python 3:
http://bugs.python.org/issue8393#msg103565
http://bugs.python.org/issue8514#msg104224

For eventual other people wanting a workaround, this is the code I used to leverage ``ctypes`` and redo what last python 3 code is doing. Any comment are welcome, this is my first go at ``ctypes``. I didn't extensively tested the code... so use at your own risk. The Gist might evolve if some people find issues:

https://gist.github.com/vaab/2ad7051fc193167f15f85ef573e54eb9

Tests/Usecases are simple: use ``subprocess.Popen(..)`` to simply issue a ``git commit -am "ć"``. And display the changelog. You can also call another python script, that would then need this other recipe (this time to get ``sys.argv`` correctly encoded on windows):

http://code.activestate.com/recipes/572200/

Hope that helps.