List comprehension scope error from Python debugger

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In Python 3, you have to use the interact command in pdb before you can access any non-global variables due to a change in the way comprehensions are implemented.

>>> def foo(): [][0]
... 
>>> foo()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in foo
IndexError: list index out of range
>>> import pdb;pdb.pm()
> <stdin>(1)foo()
(Pdb) x = 4
(Pdb) [x for _ in range(2)]
*** NameError: name 'x' is not defined
(Pdb) interact
*interactive*
>>> [x for _ in range(2)]
[4, 4]
>>>

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