#!/usr/bin/python2


import collections
import threading


class Pipe(collections.Iterable, collections.Sized):
    def __init__(self):
        self.deque = collections.deque()
        self.closed = False
        self.condition = threading.Condition()

    def put(self, element):
        with self.condition:
            if self.closed:
                raise EOFError("Pipe closed")
            self.deque.append(element)
            self.condition.notify()

    def pop(self):
        with self.condition:
            while not (self.deque or self.closed):
                self.condition.wait()
            try:
                return self.deque.popleft()
            except IndexError:
                raise EOFError("Pipe closed")

    def close(self):
        with self.condition:
            self.closed = True
            self.condition.notify_all()

    def __len__(self):
        with self.condition:
            return len(self.deque)

    def __iter__(self):
        return PipeIter(self)


class PipeIter(collections.Iterator):
    def __init__(self, pipe):
        self.pipe = pipe

    def __iter__(self):
        return self

    def next(self):
        try:
            return self.pipe.pop()
        except EOFError:
            raise StopIteration()


def main():
    pipe = Pipe()
    elements = ["Foo", "Bar"]
    for element in elements:
        pipe.put(element)
    pipe.close()
    popped = list(pipe)
    assert popped == elements

if __name__ == '__main__':
    main()