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The attached patch misses a test case.
Also how can we be sure that the '/system/build.prop' file may be guaranteed to exist on all android devices ?
It is difficult to get a reliable information on the android infrastructure when the information does not relate to the java libraries.

> Also how can we be sure that the '/system/build.prop' file may be guaranteed to exist on all android devices ?
This path is hard-coded in BioniC [1]. Though I can't find a document/relevant source codes to guarantee 'ro.build.version.release' and 'ro.build.version.sdk' is always in /system/build.prop
And the format of build.prop is not exactly INI. It supports 'import' clauses. See [2] and load_properties() function in [3]
Other options include calling `getprop` via subprocess or using C level function __system_property_get(). The first approach should always work. It's just somewhat tricky on Android 4.1 [4]. For the second option, a bad news is that it's a private API and was just removed from the latest NDK. Chromium has a workaround for that [5] and CPython may use similar approaches.
[1] https://android.googlesource.com/platform/bionic/+/master/libc/include/sys/_system_properties.h
[2] http://forum.xda-developers.com/android/general/explanation-build-prop-values-t3069341
[3] https://android.googlesource.com/platform/system/core/+/master/init/property_service.cpp
[4] https://github.com/rave-engine/python3-android/pull/10#issuecomment-159151445
[5] https://groups.google.com/a/chromium.org/forum/#!topic/chromium-reviews/keQP6L9aVyU 

The android/api-level.h header exists at all the android API levels and define __ANDROID_API__ as, for example at level 21:
 #define __ANDROID_API__ 21
So it is possible to get the sdk version from here, and maybe forget about the release version.

Isn't this macro used in compile time? I thought android_ver() aims to check runtime versions.

If the file is guaranteed to exist on most modern Android platforms, this sounds like a good approach.
Perhaps you could add support to fallback to running getprop instead, if the file doesn't exist or cannot be parsed ?!

Some screenshots showing different file contents:
 * http://www1-lw.xda-cdn.com/files/2013/12/tweak-your-samsung-galaxy-s3s-performance-with-these-build-prop-android-hacks.w654.jpg
 * http://media.apcmag.com/wp-content/uploads/sites/20/2014/04/buildprop-text-file.jpg
 * http://i.imgur.com/hZXQaX9.png
I think exposing `codename` and `incremental` may also make sense to get a complete picture.
`ro.product` also has a lot of useful entries which could be used for some of the other platform APIs such as uname().

I have a WIP patch. [1] It's based on Shiz's patch [2].
[1] https://github.com/yan12125/python3-android/blob/cpython-hg/mk/python/android-misc.patch
[2] https://github.com/rave-engine/python3-android/blob/9bb6420317922c07df405315eea040f9301f7eca/mk/python/3.4.3/python-3.4.3-android-misc.patch 

Several questions on implementation:
1. Should Android 4.1 supported? If not pass_fds and logics for deriving it can be removed.
2. I can't find ro.build.version.full on any device/emulator I have access to. Maybe it should be removed due to low popularity?
Some related Android source codes, as my implementation basis:
1. Android 4.1's ANDROID_PROPERTY_WORKSPACE: https://android.googlesource.com/platform/bionic/+/android-4.1.1_r1/libc/bionic/system_properties.c#55
2. The Android Framework assumes property values to be valid UTF-8: https://android.googlesource.com/platform/frameworks/base/+/android-5.1.1_r37/core/jni/android_os_SystemProperties.cpp#49. In fact if I feed a malformed /system/build.prop to DalvikVM, it crashes [1]
3. Google's Android Compatibility Test Suite (CTS) [2] assumes `getprop` binary is in $PATH and can be executed: https://android.googlesource.com/platform/cts/+/android-5.1.1_r37/tests/tests/os/src/android/os/cts/BuildTest.java#110
[1] https://github.com/rave-engine/python3-android/pull/10#issuecomment-159390390
[2] https://source.android.com/compatibility/cts/ 

On 04.05.2016 21:47, Chi Hsuan Yen wrote:
> 1. Should Android 4.1 supported? If not pass_fds and logics for deriving it can be removed.
According to http://www.droid-life.com/tag/distribution/ the Jelly
Bean versions (4.1, 4.2 and 4.3) still have a sizable market
share, so if it's not too much trouble, I think supporting 4.1 would
be a plus.
> 2. I can't find ro.build.version.full on any device/emulator I have access to. Maybe it should be removed due to low popularity?
Agreed.

Version 2 attached. Removed ro.build.version.full.

Android framework provides an SDK_INT field [1], which parses the value of `ro.build.version.sdk` and defaults to 0 if failed [2]. Should android_ver() return an integer for the `sdk` field, too? It simplifies the usage in #26935 and similar ones.
[1] https://android.googlesource.com/platform/frameworks/base/+/e8579b12a3c5be5fef25fc5a1c8c2c9d43e49347/core/java/android/os/Build.java#183
[2] https://android.googlesource.com/platform/frameworks/base/+/e8579b12a3c5be5fef25fc5a1c8c2c9d43e49347/core/jni/android_os_SystemProperties.cpp#66 

IMHO returning an integer for the sdk field would be better. The patch could use shutil.which() to avoid subprocess calls when getprop is not available. It would be better to use a 'try/except ValueError' clause instead of isdigit(). The OSError and UnicodeDecodeError exceptions should not be masked, as well as ValueError if sdk cannot be parsed as an int.

Version 3.
Still using a try-catch clause to enclose the subprocess call, as _syscmd_ver does the same thing.

The ro.kernel.qemu property is set to 1 on an Android emulator and 0 otherwise. I think it should be added to the list. On some threading tests where the switch interval is set to one microsecond, it is necessary to set the switch interval to a higher value when running on the qemu emulator, see the three issues:
 issue #26939: android: test_functools hangs on armv7
 issue #26940: android: test_importlib hangs on armv7
 issue #26941: android: test_threading hangs on armv7

I guess ro.kernel.qemu is not generic enough to be an item in android_ver(). In tests you can simply use _android_getprop()

Agreed, and it is not part of the versioning scheme either.

I see Xavier de Gaye uses sysconfig.get_config_var('ANDROID_API_LEVEL') is various patches. That's OK if the build-time target API level of CPython matches runtime Android API level. Does CPython force API level matching? If so this issue is no longer necessary.

ANDROID_API_LEVEL can only be used in the Python test suite and platform.android_ver() must be used in the standard library. The reason why ANDROID_API_LEVEL can be used in the tests instead of using the runtime API level is that the Python test suite purpose is not to test the compatibilities betweeen all the possible subjacent bionic libc(s) and the tests need only be run on the platform for which they have been built.
platform.android_ver() is a welcome enhancement, and since we are at 3.6 beta now it's too late for 3.6 and it will be implemented in 3.7. Sorry about this delay.

Chromium still uses the private __system_property_get() function:
https://chromium.googlesource.com/chromium/+/trunk/base/sys_info_android.cc
I would prefer a C function call rather than spawning a subprocess, just to get a value. But the function seems private, and I see discussion about removal of the function...

I cannot find a reference to the "build.prop" file in the Android documentation but google answers at the question ' what is "build.prop"':
 The "build.prop" file is a system file that exists on every Android device. The file contains build information and other system properties which are used throughout the operating system.
and stackoverflow is thriving with questions on how to edit this file.
The file contains part of the information returned by the getprop command and all the information we are needing here.
Here is its content and access rights on an android-24-x86_64 emulator:
generic_x86_64:/data/local/tmp/python $ ls -al /system/build.prop
-rw-r--r-- 1 root root 2083 2017年07月12日 22:01 /system/build.prop
generic_x86_64:/data/local/tmp/python $ cat /system/build.prop
# begin build properties
# autogenerated by buildinfo.sh
ro.build.id=NYC
ro.build.display.id=sdk_phone_x86_64-userdebug 7.0 NYC 4174735 test-keys
ro.build.version.incremental=4174735
ro.build.version.sdk=24
ro.build.version.preview_sdk=0
ro.build.version.codename=REL
ro.build.version.all_codenames=REL
ro.build.version.release=7.0
ro.build.version.security_patch=2017年06月05日
ro.build.version.base_os=
ro.build.date=Wed Jul 12 19:46:52 UTC 2017
ro.build.date.utc=1499888812
ro.build.type=userdebug
ro.build.user=android-build
ro.build.host=wphl5.hot.corp.google.com
ro.build.tags=test-keys
ro.build.flavor=sdk_phone_x86_64-userdebug
ro.product.model=Android SDK built for x86_64
ro.product.brand=Android
ro.product.name=sdk_phone_x86_64
ro.product.device=generic_x86_64
ro.product.board=
# ro.product.cpu.abi and ro.product.cpu.abi2 are obsolete,
# use ro.product.cpu.abilist instead.
ro.product.cpu.abi=x86_64
ro.product.cpu.abilist=x86_64,x86
ro.product.cpu.abilist32=x86
ro.product.cpu.abilist64=x86_64
ro.product.manufacturer=unknown
ro.product.locale=en-US
ro.wifi.channels=
ro.board.platform=
# ro.build.product is obsolete; use ro.product.device
ro.build.product=generic_x86_64
ro.product.cpu.abilist=x86_64,x86
ro.product.cpu.abilist32=x86
ro.product.cpu.abilist64=x86_64
ro.product.manufacturer=unknown
ro.product.locale=en-US
ro.wifi.channels=
ro.board.platform=
# ro.build.product is obsolete; use ro.product.device
ro.build.product=generic_x86_64
# Do not try to parse description, fingerprint, or thumbprint
ro.build.description=sdk_phone_x86_64-userdebug 7.0 NYC 4174735 test-keys
ro.build.fingerprint=Android/sdk_phone_x86_64/generic_x86_64:7.0/NYC/4174735:userdebug/test-keys
ro.build.characteristics=emulator
# end build properties
#
# from build/target/board/generic_x86_64/system.prop
#
#
# system.prop for generic sdk
#
rild.libpath=/system/lib/libreference-ril.so
rild.libargs=-d /dev/ttyS0
#
# ADDITIONAL_BUILD_PROPERTIES
#
ro.config.notification_sound=OnTheHunt.ogg
ro.config.alarm_alert=Alarm_Classic.ogg
persist.sys.dalvik.vm.lib.2=libart.so
dalvik.vm.isa.x86_64.variant=x86_64
dalvik.vm.isa.x86_64.features=default
dalvik.vm.isa.x86.variant=x86
dalvik.vm.isa.x86.features=default
dalvik.vm.lockprof.threshold=500
xmpp.auto-presence=true
ro.config.nocheckin=yes
net.bt.name=Android
dalvik.vm.stack-trace-file=/data/anr/traces.txt

"-rw-r--r-- 1 root root 2083 2017年07月12日 22:01 /system/build.prop" so
anyone can *read* the file. Maybe we can write a cheap parser for it,
instead of spawning a subprocess or relying on a private function
which may be removed in the near future?

Yes, and fall back to spawning getprop if that fails.
In the following link Robin Gawenda is reporting that /system/build.prop is world readable on all the devices he checked: https://stackoverflow.com/questions/9937099/how-to-get-the-build-prop-values 

> Yes, and fall back to spawning getprop if that fails.
I suggest to start simple. Parsing a text file is simple, spawning a subprocess can have annoying side effects :-(