[llvm-dev] Migrate utils/ Python 2 scripts to Python 3

[Chris Matthews via llvm-dev]

The suggested way to do this on OSX is using env:

#!/usr/bin/env python3

> On Jan 31, 2018, at 10:48 AM, Adrian Prantl <aprantl at apple.com> wrote:
> 
> 
> 
>> On Jan 31, 2018, at 10:04 AM, Fāng-ruì Sòng via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>> 
>> Thanks for the information. Then how about standalone scripts (many
>> one-file) like utils/update_check_tests.py that are unrelated to lit
>> or other important infrastructure? Can they be changed from
>> `#!/usr/bin/python2.7` to `#!/usr/bin/python3` shebang?
>> 
> 
> No. Every machine running macOS has /usr/bin/python and /usr/bin/python2.7 and because of system integrity protection it isn't even possible to install a python3 binary into /usr/bin (You can install it to /usr/local/bin though).
> 
> -- adrian
> 
>> On Tue, Jan 30, 2018 at 11:20 AM, Chris Matthews
>> <chris.matthews at apple.com> wrote:
>>> Personally, every machine I work with only has Python 2.7.
>>> 
>>> Justin is correct that there is a non-trivial amount of effort to convert
>>> the bots.
>>> 
>>> Python 3 is wonderful. But, a Python 3 dependency seems like one burden that
>>> could be avoided.  We have already made that trade-off in the past, for
>>> example by only using standard python packages, so there is less/nothing to
>>> pip install when getting started.  Dependencies likes host compiler and
>>> cmake totally make sense given they are central to how LLVM is made.  I
>>> don’t think the same for the python code.
>>> 
>>> I’m in favor of 2/3 compatibility until the death clock ends.
>>> 
>>> 
>>> On Jan 30, 2018, at 4:48 AM, 陳韋任 via llvm-dev <llvm-dev at lists.llvm.org>
>>> wrote:
>>> 
>>> Does Python 3 have feature we want to use in LLVM codebase, and no
>>> workaround there? If so, please give some examples. I think that makes the
>>> discussion more concrete.
>>> 
>>> 2018-01-30 4:46 GMT+08:00 Fāng-ruì Sòng via llvm-dev
>>> <llvm-dev at lists.llvm.org>:
>>>> 
>>>> Hi LLVM-Devs,
>>>> 
>>>> I noticed that many Python scripts under utils/ have a shebang of
>>>> `#!/usr/bin/python` (which is a symlink to python2.7 on many platforms)
>>>> and some of them use Python 2 syntax that is not compatible with Python 3
>>>> (e.g. print statements; str/bytes)
>>>> 
>>>> I created a revision to migrate utils/update_{llc_,}_test_checks.py from
>>>> Python 2 to Python 3 https://reviews.llvm.org/D42450 , the arguments against
>>>> making it Python 3 is:
>>>> 
>>>> * There are many Mac OS X users and Mac OS X 10.8 comes with Python 2.7
>>>> pre-installed [0] but not Python 3.
>>>> * Forcing scripts to use Python 3 (by doing so we can avoid some
>>>> compatibility trouble) may not be a good idea.
>>>> 
>>>> Python 2.7 was published in 2010 and planned as the last of the 2.x
>>>> releases. It will not be maintained past 2020 and there is also a retirement
>>>> page https://pythonclock.org/ .
>>>> 
>>>> The second argument would not need to be addressed if the first one did
>>>> not lay too much burden on developers. After all, we have to install `cmake,
>>>> ninja/GNU Make / libedit(for lldb)` to build LLVM. These packages are not
>>>> installed by default on many platforms.
>>>> 
>>>> Thoughts on deprecating Python 2 for utils/ scripts (different from
>>>> libclang or lldb scripts) which are not user-facing?
>>>> 
>>>> [0]:
>>>> https://docs.python.org/3/using/mac.html#getting-and-installing-macpython
>>>> 
>>>> 
>>>> Thanks,
>>>> Fangrui
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>> 
>>> 
>>> 
>>> 
>>> --
>>> Wei-Ren Chen (陳韋任)
>>> Homepage: https://people.cs.nctu.edu.tw/~chenwj
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>> 
>>> 
>> 
>> 
>> 
>> -- 
>> 宋方睿
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