Where is the class list_iterator defined?

Question

I would like to see the definition of the class list_iterator. When I try to display its definition with the function help I get an error. Is there a module that I have to import in order to access to its help?

More precisely, I would to know how to get a reference to the object iterable that the iterator iterates. For example:

l = [1,2,3,4,5]
it = iter(l)
print(type(it))   # this prints: list_iterator
# how to get a reference to l using it

I am pretty sure the object it has a reference to the object l. This example proves it:

import sys
l = [1,2,3,4]
print(sys.getrefcount(l))   # prints 2
it = iter(l)
print(sys.getrefcount(l))   # prints 3 

So the third reference surely came from it

Answer 1

Does garbage collection's get_referents do it for you?

import gc

l = [1,2,3,4,5]
it = iter(l)

refs = gc.get_referents(it)  # looks like: [[1, 2, 3, 4, 5]]
assert l in refs  # True
assert l == refs[0]  # True

EDIT: It should be noted that the reference to l disappears when it is exhausted and raises StopIteration. So when you finish iterating over it, the reference-check above fails. This can be a feature or a bug depending on your use case but you should be aware of it.

# Exhaust the iterator
for x in it:
    pass

refs = gc.get_referents(it)
assert l not in refs  # No more reference to l
assert not refs  # No more reference to anything actually