The loop - play.py

# play.py from types import coroutine from collections import deque from selectors import DefaultSelector, EVENT_READ, EVENT_WRITE @coroutine def read_wait(sock): yield 'read_wait', sock @coroutine def write_wait(sock): yield 'write_wait', sock class Loop: def __init__(self): self.ready = deque() self.selector = DefaultSelector() async def sock_recv(self, sock, maxbytes): await read_wait(sock) return sock.recv(maxbytes) async def sock_accept(self, sock): await read_wait(sock) return sock.accept() async def sock_sendall(self, sock, data): while data: try: nsent = sock.send(data) data = data[nsent:] except BlockingIOError: await write_wait(sock) def create_task(self, coro): self.ready.append(coro) def run_forever(self): while True: while not self.ready: events = self.selector.select() for key, _ in events: self.ready.append(key.data) self.selector.unregister(key.fileobj) while self.ready: self.current_task = self.ready.popleft() try: op, *args = self.current_task.send(None) # Run to the yield getattr(self, op)(*args) # Sneaky method call except StopIteration: pass def read_wait(self, sock): self.selector.register(sock, EVENT_READ, self.current_task) def write_wait(self, sock): self.selector.register(sock, EVENT_WRITE, self.current_task)