On 28. 03. 22 15:25, Irit Katriel via Python-Dev wrote:
If you have a __future__ import in a script, and you import * from it in
another script, the object for this future appears in the dir() of the
other script, even though the __future__ import has no effect there.
% cat x.py
from __future__ import annotations
% cat y.py
from x import *
print(dir())
class D:
def f(self, a: D):
return 42
% ./python.exe y.py
['__annotations__', '__builtins__', '__cached__', '__doc__', '__file__',
'__loader__', '__name__', '__package__', '__spec__', '*annotations*']
Traceback (most recent call last):
File "/Users/iritkatriel/src/cpython-654/y.py", line 5, in <module>
class D:
^^^^^^^^
File "/Users/iritkatriel/src/cpython-654/y.py", line 6, in D
def f(self, a: D):
^
NameError: name 'D' is not defined
I think we should change import * to exclude the __future__ import
objects, and perhaps also to not show them in dir(x). Any objections?
This came up in the discussion about https://bugs.python.org/issue26120
<https://bugs.python.org/issue26120> . See the attached PR for a
technique we can use to identify those objects.
__future__ imports are just one way to put garbage in the global
namespace. I don't think they should be handled specially.
IMO, it would be better to document the current best practice that
`import *` should only be used with modules designed for `import *` (by
setting `__all__`; carefully `del`-ing what they don't want to export
might work too but it's fragile), or when you don't care about namespace
pollution (e.g. in interactive sessions).
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