python - gevent socket怎么能只阻塞当前的greenlet？

Question

我正在阅读gevent.socket，但我不明白。

def recv(self, *args):
    sock = self._sock  # keeping the reference so that fd is not closed during waiting
    while True:
        try:
            return sock.recv(*args)
        except error, ex:
            if ex[0] == EBADF:
                return ''
            if ex[0] != EWOULDBLOCK or self.timeout == 0.0:
                raise
            # QQQ without clearing exc_info test__refcount.test_clean_exit fails
            sys.exc_clear()
        try:
            wait_read(sock.fileno(), timeout=self.timeout, event=self._read_event)
        except error, ex:
            if ex[0] == EBADF:
                return ''
            raise

sockin是的recv一个实例_realsocket(family, type, proto)。在socket.py中我发现：

import _socket
_realsocket = _socket.socket

什么是_socket？为什么不return sock.recv(*args)阻止整个程序？

Answer 1

_socket 是python的标准c库，提供真正的网络通信，socket.py（在标准库或gevent中）包装了常用的方法。

然后，查看gevent.socket中类 Socket 的初始化，

```self._sock.setblocking(0)```

此语句使套接字对象非阻塞