python学习之hook钩子的原理和使用

什么是钩⼦

之前有转⼀篇关于回调函数的

钩⼦函数、注册函数、回调函数，他们的概念其实是⼀样的。

钩⼦函数，顾名思义，就是把我们⾃⼰实现的hook函数在某⼀时刻挂接到⽬标挂载点上。 1. hook函数，就是我们⾃⼰实现的函数，函数类型与挂载点匹配（返回值，参数列表） 2. 挂接，也就是hook或者叫注册（register）,使得hook函数对⽬标可⽤

3. ⽬标挂载点，也就是挂我们hook函数的地⽅（我们想在这个⽬标点实现我们⾃⼰的功能） 先看⼀张图：

hook的概念在windows的消息响应机制⾥⾯体现的尤为明显。可能我们⼤家有写过windows桌⾯相关的程序（像MFC），⾥⾯有各种消息监听响应机制。⽐如，要监听⿏标左键是否按下这个事件，我们要去实现⼀个onLeftKeyDown（）之类的⽅法，该⽅法可以称为钩⼦函数。同时，我们还要去注册钩⼦函数，MFC中是通过⼀组宏来实现的。这样当⿏标左键按下后，就能调到我们定义的⽅法了。为什么需要钩⼦

⼤家思考⼀下上⾯这个例⼦，左键按下⽅法具体的逻辑是由框架⾃⾝去实现，还是由我们⽤户（调⽤者）去实现呢？显然应该由我们⾃⼰去实现。要提供通⽤的框架能⼒，框架⾃⾝去实现该⽅法功能，是没有意义的，所以框架给提供⼀个挂载的point，把具体逻辑的实现交给⽤户就好了，灵活可⽤。 钩⼦使⽤

hook是⼀个编程机制，与语⾔⽆关。这⾥给个python的简单例⼦，帮助⼤家理解：

import time

class LazyPerson(object): def __init__(self, name): self.name = name

self.watch_tv_func = None self.have_dinner_func = None

def get_up(self):

print(\"%s get up at:%s\" % (self.name, time.time())) def go_to_sleep(self):

print(\"%s go to sleep at:%s\" % (self.name, time.time())) def register_tv_hook(self, watch_tv_func): self.watch_tv_func = watch_tv_func

def register_dinner_hook(self, have_dinner_func): self.have_dinner_func = have_dinner_func def enjoy_a_lazy_day(self):

# get up self.get_up() time.sleep(3) # watch tv

# check the watch_tv_func(hooked or unhooked) # hooked

if self.watch_tv_func is not None: self.watch_tv_func(self.name) # unhooked else:

print(\"no tv to watch\") time.sleep(3) # have dinner

# check the have_dinner_func(hooked or unhooked) # hooked

if self.have_dinner_func is not None: self.have_dinner_func(self.name)

# unhooked else:

print(\"nothing to eat at dinner\") time.sleep(3)

self.go_to_sleep()

def watch_daydayup(name):

print(\"%s : The program ---day day up--- is funny\" % name)def watch_happyfamily(name):

print(\"%s : The program ---happy family--- is boring\" % name)def eat_meat(name):

print(\"%s : The meat is nice\" % name)

def eat_hamburger(name):

print(\"%s : The hamburger is not so bad\" % name)

if __name__ == \"__main__\": lazy_tom = LazyPerson(\"Tom\") lazy_jerry = LazyPerson(\"Jerry\") # register hook

lazy_tom.register_tv_hook(watch_daydayup) lazy_tom.register_dinner_hook(eat_meat)

lazy_jerry.register_tv_hook(watch_happyfamily) lazy_jerry.register_dinner_hook(eat_hamburger) # enjoy a day

lazy_tom.enjoy_a_lazy_day() lazy_jerry.enjoy_a_lazy_day()

代码运⾏结果：

Tom get up at:1509246940.32

Tom : The program ---day day up--- is funnyTom : The meat is nice

Tom go to sleep at:1509246949.34Jerry get up at:1509246949.34

Jerry : The program ---happy family--- is boringJerry : The hamburger is not so badJerry go to sleep at:1509246958.37

以上就是本⽂的全部内容，希望对⼤家的学习有所帮助，也希望⼤家多多⽀持。