New submission from Chris Billington <[email protected]>:
The following one-liner works fine in a regular Python interpreter:
$ python -c 'import sys; x = 5; [print(x + i) for i in range(5)]'
5
6
7
8
9
But in a .pth file, it raises a NameError:
$ echo 'import sys; x = 5; [print(x + i) for i in range(5)]' | sudo tee
/usr/lib/python3.8/site-packages/test.pth
$ python
Error processing line 1 of /usr/lib/python3.8/site-packages/test.pth:
Traceback (most recent call last):
File "/usr/lib/python3.8/site.py", line 169, in addpackage
exec(line)
File "<string>", line 1, in <module>
File "<string>", line 1, in <listcomp>
NameError: name 'x' is not defined
Remainder of file ignored
Python 3.8.0 (default, Oct 23 2019, 18:51:26)
[GCC 9.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
Since site.py uses exec() to exec each line of a .pth file, I thought I'd
compare with that. It also works fine:
$ python -c 'exec("import sys; x = 5; [print(x + i) for i in range(5)]")'
5
6
7
8
9
This slight modification (the variable being used in the next statement still,
but not within the loop of the comprehension) does not raise a NameError:
$ echo 'import sys; x = 5; [print(i) for i in range(x)]' | sudo tee
/usr/lib/python3.8/site-packages/test.pth
import sys; x = 5; [print(i) for i in range(x)]
$ python
0
1
2
3
4
Python 3.8.0 (default, Oct 23 2019, 18:51:26)
[GCC 9.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
I know .pth file processing is very early in interpreter startup such that many
things aren't working yet, but I wouldn't expect using a name defined outside a
list comprehension within the loop body of said list comprehension not to work.
The following is fine also, showing that using names from outside the list
comprehension doesn't always break:
$ echo 'import sys; [print(sys) for i in range(5)]' | sudo tee
/usr/lib/python3.8/site-packages/test.pth
import sys; [print(sys) for i in range(5)]
$ python
<module 'sys' (built-in)>
<module 'sys' (built-in)>
<module 'sys' (built-in)>
<module 'sys' (built-in)>
<module 'sys' (built-in)>
Python 3.8.0 (default, Oct 23 2019, 18:51:26)
[GCC 9.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
This is fine too:
$ echo 'import sys; [print(str(sys) * i) for i in range(5)]' | sudo tee
/usr/lib/python3.8/site-packages/test.pth
import sys; [print(str(sys) * i) for i in range(5)]
$ python
<module 'sys' (built-in)>
<module 'sys' (built-in)><module 'sys' (built-in)>
<module 'sys' (built-in)><module 'sys' (built-in)><module 'sys' (built-in)>
<module 'sys' (built-in)><module 'sys' (built-in)><module 'sys'
(built-in)><module 'sys' (built-in)>
Python 3.8.0 (default, Oct 23 2019, 18:51:26)
[GCC 9.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
My use case is looping over subdirs of a directory and adding them all to
sys.path to provide similar functionality to python setup.py develop, with all
python vcs repositories within a specific directory being prepended to
sys.path, rather than having to add them one-by-one. I probably won't end up
doing what I'm doing this way, but in any case the above seems like it's a bug,
unless I'm grossly misunderstanding something.
----------
components: Interpreter Core
messages: 357627
nosy: Chris Billington
priority: normal
severity: normal
status: open
title: NameError in list comprehension within .pth file
versions: Python 3.8
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Python tracker <[email protected]>
<https://bugs.python.org/issue38937>
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