What are python closures?

Python closures mainly include function closures and decorator closures. Detailed introduction: 1. Function closure refers to returning another function inside a function, and the returned function can access its internal variables. Such a returned function is a function closure. Function closures can be used repeatedly in the program, so they can be used to implement some functional encapsulation; 2. Decorator closure means that when using a decorator, the decorated function is not It is not called directly, but is wrapped inside a function and returns a new function. This new function is a decorator closure and so on.

The operating system for this tutorial: windows system, python version 3.11.4, Dell G3 computer.

Closures in Python mainly include two types: function closures and decorator closures.

Function closure: Function closure means returning another function inside a function, and the returned function can access its internal variables. Such a returning function is a function closure. Function closures can be used repeatedly in the program, so they can be used to implement some functional encapsulation.

The following is a simple example:

def outer():  
    x = 10  
    def inner():  
        print(x)  
    return inner  
  
f = outer()  # 创建函数闭包  
f()  # 调用函数闭包

In this code, outer The function returns a closure of the inner function. We can call f() repeatedly to access the variable x in the closure.

Decorator closure: Decorator closure means that when using a decorator, the decorated function is not called directly, but is wrapped inside a function and returned a new function. This new function is a decorator closure. Decorator closures are often used to implement functionality enhancement, logging and other functions.

The following is a simple example:

def my_decorator(func):  
    def wrapper():  
        print("Before the function is called.")  
        func()  # 调用被装饰的函数  
        print("After the function is called.")  
    return wrapper  
  
@my_decorator  
def say_hello():  
    print("Hello!")  
  
say_hello()  # 调用装饰后的函数

In this code, my_decorator Is a decorator that wraps the say_hello function and returns a new function wrapper. When we call say_hello(), we actually call the decorator closure wrapper().

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