An (partial) asyncio version of threads.Barrier. There's only wait(), no reset() or abort() or concept of being broken, and like all other asyncio->threading analogues, no timeouts.

barrier.py

import asyncio

class Barrier():
    """asyncio version of threading.Barrier (partial).
    
    Implements wait() only, without support for timeouts."""
    
    def __init__(self, parties, loop=None):
        if loop is None:
            self._loop = asyncio.get_event_loop()
        else:
            self._loop = loop
        self.parties = parties
        self.n_waiting = 0
        self._master_fut = asyncio.Future(loop=self._loop)
    
    @asyncio.coroutine
    def wait(self):
        n = self.n_waiting
        self.n_waiting += 1
        
        if self.n_waiting > self.parties:
            raise RuntimeError('Barrier already passed')
        
        if self.n_waiting == self.parties:
            self._master_fut.set_result(None)
        
        yield from self._master_fut
        
        return n