extras.py 文件源码

def wait_select(conn):
    """Wait until a connection or cursor has data available.

    The function is an example of a wait callback to be registered with
    `~psycopg2.extensions.set_wait_callback()`. This function uses
    :py:func:`~select.select()` to wait for data available.

    """
    import select
    from psycopg2.extensions import POLL_OK, POLL_READ, POLL_WRITE

    while 1:
        state = conn.poll()
        if state == POLL_OK:
            break
        elif state == POLL_READ:
            select.select([conn.fileno()], [], [])
        elif state == POLL_WRITE:
            select.select([], [conn.fileno()], [])
        else:
            raise conn.OperationalError("bad state from poll: %s" % state)