[Python-Dev] Exposing the Android platform existence to Python modules (original) (raw)

Shiz hi at shiz.me
Sat Aug 2 14:00:04 CEST 2014

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Akira Li wrote:

Python uses os.name, sys.platform, and various functions from platform module to provide version info:

- coarse: os.name is 'posix', 'nt', 'ce', 'java' [1]. It is defined by availability of some builtin modules ('posix', 'nt' in particular) at import time. - finer: sys.platform may start with freebsd, linux, win, cygwin, darwin (uname -s). It is defined at python build time. - detailed: platform module. It provides as much info as possible e.g., platform.uname(), platform.platform(). It may use runtime commands to get it. If Android is posixy enough (would posix module work on Android?) then os.name could be left 'posix'. You could set sys.platform to 'android' (like sys.platform may be 'cygwin' on Windows) if Android is not like any other Linux distribution (from the point of view of writing a working Python code on it) i.e., if Android is further from other Linux distribution than freebsd, linux, darwin from each other then it might deserve sys.platform slot. If sys.platform is left 'linux' (like sys.platform is 'darwin' on iOS) then platform module could be used to detect Android e.g., platform.linuxdistribution() though (it might be removed in Python 3.6) it is unpredictable [2] unless you fix it on your python distribution, e.g., here's an output on my machine:

import platform platform.linuxdistribution() ('Ubuntu', '14.04', 'trusty') For example: isandroid = (platform.linuxdistribution()[0] == 'Android') You could also define platform.androidversion() that can provide Android specific version details as much as you need: isandroid = bool(platform.androidversion().release) You could provide an alias androidver (like existing javaver, libcver, macver, win32ver). See also, "When to use os.name, sys.platform, or platform.system?" [3] Unrelated, TIL [4]: Android is a Linux distribution according to the Linux Foundation [1] https://docs.python.org/3.4/library/os.html#os.name [2] http://bugs.python.org/issue1322 [3] http://stackoverflow.com/questions/4553129/when-to-use-os-name-sys-platform-or-platform-system [4] http://en.wikipedia.org/wiki/Android_(operating_system) btw, does it help adding os.getshellexecutable() [5] function, to avoid hacking subprocess module, so that os.confstr('CSPATH') or os.defpath on Android could be defined to include /system/bin instead? [5] http://bugs.python.org/issue16353

Thanks for the detailed information!

I would consider Android at least POSIX-y enough for os.name to be considered 'posix'. It doesn't implement a few POSIX-mandated things like POSIX semaphores, but aside from that I would largely consider it 'compatible enough'.

I guess what is left is deciding whether to add a platform slot for Android, or to stuff the detection in platform.linux_distribution(). I feel like it would be a bit hacky for standard modules to rely on a platform.linux_distribution() return value though, it seems mostly useful for display purposes.

Phil Thompson's idea of setting sys.platform to 'linux-android' also occurred to me. Under the premise that we can get users to use sys.platform.startswith('linux'), this seems like the best solution in my eyes: it both allows for existing code to continue the assumption that they are running on a Linux platform, which I believe to be correct in a lot of places, and Python modules to use a solid value to check if they need to behave differently when running on Android.

On a sidenote, Kivy and SL4A/Py4A do not address this, no. From what I've seen from their patches they are mostly there to get Python compiling and running in the first place, not necessarily about fixing every compatibility issue. :)

As for the os.get_shell_executable(), that seems like a good solution for the issue that occurs in the subprocess module indeed. I'd personally prefer it to manual checking within the module.

Kind regards, Shiz -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.22 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

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