1.Hooking为何物？

In computer programming， the term hooking covers a range of techniques used to alter or augment the behavior of an operating system， of applications， or of other software components by intercepting function calls or messages or events passed between software components. Code that handles such intercepted function calls， events or messages is called a hook.

Hooking is used for many purposes， including debugging and extending functionality. Examples might include intercepting keyboard or mouse event messages before they reach an application， or intercepting operating system calls in order to monitor behavior or modify the function of an application or other component.

Hooking can also be used by malicious code. For example， rootkits， pieces of software that try to make themselves invisible by faking the output of API calls that would otherwise reveal their existence， often use hooking techniques. A wallhack is another example of malicious behavior that can stem hooking techniques. It is done by intercepting function calls in a computer game and altering what is shown to the player to allow them to gain an unfair advantage over other players.

ref：http://en.wikipedia.org/wiki/Hooking

2.Hooking in Python

Hooks are generally callbacks， yes. Callbacks in python are simply done by passing functions around and calling them. Hooking is a way to get your own code to execute when another system is running， whether that other system is an OS， a GUI， or whatever. A somewhat silly example in Python:

def Process（records， per_record_hook=None）:

    adds all records to XYZ system

    for record in records:

        if per_record_hook:

            per_record_hook（record）

        XYZ.append（record）



def print_record（record）:

    print a . for each record （primitive counter）

    print .

and then later:

Process（records__somewhere， per_record_hook=print_record）

感谢浏览！