Python iter() built-in function

From the Python 3 documentation Return an iterator object. The first argument is interpreted very differently depending on the presence of the second argument. Without a second argument, object must be a collection object which supports the iterable protocol, or it must support the sequence protocol. If it does not support either of those protocols, TypeError is raised.

Examples¶

>>> i = iter([1, 2, 3])
>>> i
# <list_iterator object at 0x7f93158badc0>
>>> i.__next__()
# 1
>>> i.__next__()
# 2
>>> i.__next__()
# 3