python的callback函数原理

__getattribute__作用

"""
class C(object):
    a = 'abc'
    def __getattribute__(self, *args, **kwargs):
        print("__getattribute__() is called")
        print args
        if args[0] == 'a':
            return object.__getattribute__(self, *args, **kwargs)
        else:
            print '调用函数foo()'
            return object.__getattribute__(self,'foo')()
    def foo(self):
        return "hello"
if __name__ == '__main__':
    c = C()
    print c.foo
"""

callback

class Callback:
    def __init__(self, instance, function_name):
        self.instance = instance # api.self
        self.function_name = function_name # function
 
    def action(self, params):
        print self.instance.__getattribute__(self.function_name)
        self.instance.__getattribute__(self.function_name)(params)
 
class Test:
    def __init__(self):
        self.clb = None
 
    def register(self, clb):
        self.clb = clb # Callback(self, self.function.__name__)
 
    def do_test(self):
        params = []
        self.clb.action(params)
 
class Api(object):
    def __init__(self, test_instance):
        test_instance.register(Callback(self, self.function.__name__))
 
    def function(self, params):
        print params
        print('function')
 
t = Test()
a = Api(t)
t.do_test()

第二种callback制造方法

import errno
import functools
import tornado.ioloop
import socket
 
def connection_ready(sock, fd, events):
    while True:
        try:
            connection, address = sock.accept()
        except socket.error as e:
            if e.args[] not in (errno.EWOULDBLOCK, errno.EAGAIN):
                raise
            return
        connection.setblocking()
        handle_connection(connection, address)
 
if __name__ == '__main__':
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, )
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, )
    sock.setblocking()
    sock.bind(("", port))
    sock.listen()
 
    io_loop = tornado.ioloop.IOLoop.current()  # IOLoop()
    callback = functools.partial(connection_ready, sock)
    io_loop.add_handler(sock.fileno(), callback, io_loop.READ)
    io_loop.start()

还有一种比较不错的回调函数