locally imported modules are unaccessible in lambdas in pdb #76987

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1. YuriKanivetsky commented on Feb 9, 2018

   

   YuriKanivetskymannequin

   on Feb 9, 2018

   MannequinAuthor

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   Consider the following script:

       # import pdb; pdb.set_trace()
       # import re
       def f():
           import re
           print((lambda: re.findall('a', 'aaa'))())
           import pdb; pdb.set_trace()
           print('test')
       f()

   When you run it and try to evaluate (lambda: re.findall('a', 'aaa'))(), you get:

   ['a', 'a', 'a']
   > /home/yuri/_/1.py(7)f()
   -> print('test')
   (Pdb) (lambda: re.findall('a', 'aaa'))()
   *** NameError: name 're' is not defined
   (Pdb) import re
   (Pdb) (lambda: re.findall('a', 'aaa'))()
   *** NameError: name 're' is not defined
   (Pdb) 
   

   With the commented out breakpoint it works:

   > /home/yuri/_/a.py(3)<module>()
   -> def f():
   (Pdb) import re
   (Pdb) (lambda: re.findall('a', 'aaa'))()
   ['a', 'a', 'a']
   (Pdb) 
   

   Also it works with uncommented global import and second breakpoint:

   ['a', 'a', 'a']
   > /srv/http/sl/makosh/a.py(7)f()
   -> print('test')
   (Pdb) (lambda: re.findall('a', 'aaa'))()
   ['a', 'a', 'a']
   (Pdb) 
   

   From what I can see the issue occurs when there's no re in globals argument here: https://github.com/python/cpython/blob/v3.6.4/Lib/pdb.py#L376

   I've run into it when trying to grep some object's attribute names, like:

   !list(filter(lambda x: re.search('class', x), dir(__name__)))
   
2. YuriKanivetsky

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Feb 9, 2018
3. nitishch commented on Feb 11, 2018

   

   nitishchmannequin

   on Feb 11, 2018

   Mannequin

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   This can be traced back to the following issue:

   >>> c = compile("(lambda: re.findall('a', 'aaa'))()", "<stdin>", "single")
   >>> import re as rea
   >>> exec(c, None, {'re': rea})
   NameError: name 're' is not defined.

   Seeing disassembly of the compiled code, it used LOAD_GLOBAL to get re. This seems to be the problem.
4. nitishch commented on Feb 11, 2018

   

   nitishchmannequin

   on Feb 11, 2018

   Mannequin

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   Sorry. I didn't finish my last message. Is the behaviour described in that message a bug? If yes, that would explain the original behaviour. If no, why not?
5. ezio-melotti

   transferred this issue fromon Apr 10, 2022
6. iritkatriel

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   on Nov 23, 2023
7. gaogaotiantian commented on May 6, 2024

   

   gaogaotiantian

   on May 6, 2024

   Member

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   Fixed by #111094
8. gaogaotiantian

   closed this as completedon May 6, 2024