Simplistic Queue implementation

simplequeue.py

'''
Very simple queue implementation. Don't use it. Use collections.deque
instead.

>>> q = Queue()
>>> q.push(1)
>>> q.push(2)
>>> len(q)
2
>>> bool(q)
True
>>> q.pop()
1
>>> q.push(3)
>>> len(q)
2
>>> q.pop()
2
>>> q.push(4)
>>> q.pop()
3
>>> q.pop()
4
>>> len(q)
0
>>> bool(q)
False
>>> q.pop()
Traceback (most recent call last):
 ...
IndexError: pop from empty list
'''

class Queue(object):
    def __init__(self):
        self.f, self.b = [], []

    def push(self, e):
        self.b.append(e)

    def pop(self):
        if not self.f and self.b:
            self.b.reverse()
            self.f, self.b = self.b, []
        return self.f.pop()

    def __len__(self):
        return len(self.f + self.b)

    def __nonzero__(self):
        return bool(len(self))