On 3/25/2019 12:27 AM, Cameron Simpson wrote:
> On 24Mar2019 23:22, Terry Reedy <tjreedy at udel.edu> wrote:
>> On 3/24/2019 10:01 PM, Terry Reedy wrote:
>>> On 3/24/2019 7:00 PM, Cameron Simpson wrote:
>>>> Did you have a specific scenario in mind?
>>>
>>> I was thinking about IDLE and its tangled web of circular inports,
>>> but I am now convinced that this change will not affect it. Indeed,
>>> idlelib/pyshell.py already implements idea of the proposal, ending with
>>>
>>> if __name__ == "__main__":
>>> sys.modules['pyshell'] = sys.modules['__main__']
>>> main()
>>
>> After more investigation, I realized that to stop having duplicate
>> modulue:
>> 1. The alias should be 'idlelib.pyshell', not 'pyshell', at least when
>> imports are all absolute.
>
> The PEP499 patch effectively uses __main__.__spec__.name for the name of
> the alias. Does that simplify your issue?
>
> The current PR is here if you want to look at it:
>
> https://github.com/python/cpython/pull/12490
The new test passes on Win10.
>> 2. It should be done at the top of the file, before the import of
>> modules that import pyshell.
>
> Hmm, if PEP499 comes in you shouldn't need to do this at all. If PEP499
> gets delayed or rejected I guess you're supporting this without it. Yes,
> you'll want to do it before any other imports happen (well, as you say,
> before any which import pyshell).
>
> What about (untested):
>
> if __name__ == '__main__':
> if __spec__.name not in sys.modules:
When I start pyshell in my master repository directory on windows with
python -m idlelib.pyshell
__spec__.name is 'idlelib.pyshell, which I currently hard-coded.
When I start with what should be equivalent
python f:/dev/3x/lib/idlelib/pyshell.py
__spec__ is None and __spec__.name an attribute error.
> sys.modules[__spec__.name] = sys.modules['__main__']
>
> as a forward compatible setup?
>
>> If I run python f:/dev/3x/lib/idlelib/pyshell.py, the PEP patch would
>> have to notice that pyshell is a module within idlelib and alias
>> '__main__' to 'idlelib.pyshell', not 'pyshell'. Would the same be
>> true if within-package import were all relative?
>
> I think so because we're using .__spec__.name, which I though was post
> import name resolution.
You must be doing something different when __spec__ is None ;-). I
tested the patch and it does not raise AttributeError with the command
above.
> Testing in my PEP499 branch:
>
> Test 1:
>
> [~/src/cpython-cs at github(git:PEP499-cs)]fleet*> ./python.exe -i
> Lib/idlelib/pyshell.py
> Traceback (most recent call last):
> File "<string>", line 1, in <module>
> ModuleNotFoundError: No module named 'run'
This is because of an obsolete 'command = ...' around 420. The if line
is correct always and the if/then not needed.
> >>> sys.modules['__main__']
> <module '__main__' (<_frozen_importlib_external.SourceFileLoader
> object at 0x1088e6040>)>
> >>> sys.modules['pyshell']
> <module '__main__' (<_frozen_importlib_external.SourceFileLoader
> object at 0x1088e6040>)>
> >>> sys.modules['idlelib.pyshell']
> <module 'idlelib.pyshell' from
> '/Users/cameron/src/cpython-cs at github/Lib/idlelib/pyshell.py'>
>
> So pyshell and idlelib.pyshell are distinct here.
I verified that the module was being executed twice by putting
print('running') at the top.
__main__ and pyshell
> are the same module, courtesy of your sys.modules assignment at the
> bottom of pyshell.py.
Obsolete and removed.
Test 3 below will be with that commented out.
>
> Test 2:
>
> [~/src/cpython-cs at github(git:PEP499-cs)]fleet*> PYTHONPATH=$PWD/Lib
> ./python.exe -i -m idlelib.pyshell
> Traceback (most recent call last):
> File "<string>", line 1, in <module>
> ModuleNotFoundError: No module named 'run'
> >>> sys.modules['__main__']
> <module 'idlelib.pyshell' from
> '/Users/cameron/src/cpython-cs at github/Lib/idlelib/pyshell.py'>
> >>> sys.modules['pyshell']
> <module 'idlelib.pyshell' from
> '/Users/cameron/src/cpython-cs at github/Lib/idlelib/pyshell.py'>
> >>> sys.modules['idlelib.pyshell']
> <module 'idlelib.pyshell' from
> '/Users/cameron/src/cpython-cs at github/Lib/idlelib/pyshell.py'>
> >>> id(sys.modules['__main__'])
> 4551072712
> >>> id(sys.modules['pyshell'])
> 4551072712
> >>> id(sys.modules['idlelib.pyshell'])
> 4551072712
>
> So this has __main__ and idlelib.pyshell the same module from the PEP499
> patch and pyshell also the same from your sys.modules assignment.
>
> Test 3, with the pyshell.py sys.modules assignment commented out:
>
> [~/src/cpython-cs at github(git:PEP499-cs)]fleet*> PYTHONPATH=$PWD/Lib
> ./python.exe -i -m idlelib.pyshell
> Traceback (most recent call last):
> File "<string>", line 1, in <module>
> ModuleNotFoundError: No module named 'run'
> >>> sys.modules['__main__']
> <module 'idlelib.pyshell' from
> '/Users/cameron/src/cpython-cs at github/Lib/idlelib/pyshell.py'>
> >>> sys.modules['pyshell']
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> KeyError: 'pyshell'
> >>> sys.modules['idlelib.pyshell']
> <module 'idlelib.pyshell' from
> '/Users/cameron/src/cpython-cs at github/Lib/idlelib/pyshell.py'>
> >>> id(sys.modules['__main__'])
> 4552379336
> >>> id(sys.modules['idlelib.pyshell'])
> 4552379336
>
> Here we've got __main__ and idlelib.pyshell the same module and no
> 'pyshell' in sys.modules.
> I don't think I understand your "relative import" scenario.
If files other that pyshell used relative 'import ./pyshell' instead of
absolute 'import idlelib.pyshell', would the sys.modules key still be
'idlelib.pyshell' or 'pyshell'? Which is to ask, would the alias
needed to avoid a second pyshell module still be 'idlelib.pyshell' or
'pyshell'?
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