[Python-Dev] Exposing the Android platform existence to Python modules

[Shiz]

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Guido van Rossum wrote:
> sys.platform is for a broad indication of the OS kernel. It can be
> used to distinguish Windows, Mac and Linux (and BSD, Solaris etc.).
> Since Android is Linux it should have the same sys.platform as other
> Linux systems ('linux2'). If you want to know whether a specific
> syscall is there, check for the presence of the method in the os
> module.
> 
> The platform module is suitable for additional vendor-specific info 
> about the platform, and I'd hope that there's something there that 
> indicates Android. Again, what values does the platform module return
> on SL4A or Kivy, which have already ported Python to Android? In 
> particular, I'd expect platform.linux_distribution() to return a
> clue that it's Android. There should also be clues in
> /etc/lsb-release (assuming Android supports it :-).
> 
> -- --Guido van Rossum (python.org/~guido <http://python.org/~guido>)

To the best of my knowledge, Kivy and Py4A/SL4A don't modify that code
at all, so it just returns 'linux2'. In addition, they don't modify
platform.py either, so platform.linux_distribution() returns empty values.

My patchset[1] currently contains patches that both set sys.platform to
'linux-android' and modifies platform.linux_distribution() to parse and
return a proper value for Android systems:

>>> import sys, platform sys.platform
'linux-android'
>>> platform.linux_distribution()
('Android', '4.4.2', 'Blur_Version.174.44.9.falcon_umts.EURetail.en.EU')

The sys.platform thing was mainly done out of curiosity on its
possibility after Phil bringing it up. My main issue with leaving
Android detection to checking platform.linux_distribution() is that it
feels like a bit of a wonky thing for core Python modules to rely on to
change behaviour where needed on Android (as well as introducing a
dependency cycle between subprocess and platform right now).

I'd also like to note that I wouldn't agree with following too many of
Kivy/Py4A/SL4A's design decisions on this, as they seem mostly absent.
- From what I've read, their patches mostly seem geared towards getting
Python to run on Android, not necessarily integrating it well or fixing
all inconsistencies. This also leads to things like subprocess.Popen()
indeed breaking with shell=True[2].

Kind regards,
Shiz

[1]: https://github.com/rave-engine/python3-android/tree/master/src
[2]:
http://grokbase.com/t/gg/python-for-android/1343rm7q1w/py4a-subprocess-popen-oserror-errno-8-exec-format-error
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