Python 2.7: Determining the length when using next with a python Iterator

Question

I am performing the following extraction and it is working:

>>> lines = ["cat 23\n", "dog 11\n"]
>>> "".join(lines).split()
['cat', '23', 'dog', '11']
>>> data = iter("".join(lines).split())
>>> [(next(data), next(data)) for i in range(2)]
[('cat', '23'), ('dog', '11')]

However if I change lines to be equals to:

lines = ["cat 23\n"]

I get a StopIteration with no list produced.

EDIT: As with the responses below, the answer was because I was using 2 instead of 1. is there a way to get the length of an iterator without consuming it?

Answer 1

That list comprehension is basically:

l = list()
l.append((next(data), next(data)))
l.append((next(data), next(data)))

You are calling next(data) four times on an iterator that evidently gives only two elements.

Answer 2

You specified two pairs when iterating when it should be one to reflect your list of lines:

size = len("".join(lines).split()) # size of list
[(next(data), next(data)) for i in range(size / 2)]