Pylint says
W: 6: Using possibly undefined loop variable 'n'
... with this code:
iterator = (i*i for i in range(100) if i % 3 == 0)
for n, i in enumerate(iterator):
do_something(i)
print n
because if the iterator is empty (for example []
) n
is undefined, ok. But I like this trick. How to use it in a safe way?
I think that using len(list(iterator))
is not the best choice because you have to do two loops. I think that开发者_JAVA百科 using a counter and incrementing it is not very pythonic.
Have you considered merely initializing n
to None
before running the loop?
Define a default value for n
before the for
statement:
iterator = (i*i for i in range(100) if i % 3 == 0)
n=None
for n, i in enumerate(iterator):
do_something(i)
print n
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