python补充学习.装饰器

Posted 2021-07-18 qq_51102350

装饰器

• 一，定义和功能
• 二，@修饰符
• 三，functools.wraps()函数
• 四，使用蓝本

一，定义和功能

把一个函数作为参数，返回一个替代版的函数
本质上是一个返回函数的参数

在不改变原函数的基础上，给函数增加新的功能

二，@修饰符

def a_new_decorator(a_func):
    def wrapTheFunction():
        print("I am doing some boring work before executing a_func()")

        a_func()

        print("I am doing some boring work after executing a_func()")

    return wrapTheFunction

@a_new_decorator
def a_function_requiring_decoration():
    print("I am the function which needs some decoration to remove my foul smell")

a_function_requiring_decoration()

相当于：

def a_new_decorator(a_func):
    def wrapTheFunction():
        print("I am doing some boring work before executing a_func()")

        a_func()

        print("I am doing some boring work after executing a_func()")

    return wrapTheFunction


def a_function_requiring_decoration():
    print("I am the function which needs some decoration to remove my foul smell")

a_function_requiring_decoration = a_new_decorator(a_function_requiring_decoration)

a_function_requiring_decoration()

三，functools.wraps()函数

问题：

print(a_function_requiring_decoration.__name__)
# Output: wrapTheFunction

希望输出a_function_requiring_decoration，但输出了wrapTheFunction
可见a_function_requiring_decoration被wrapTheFunction替代了

此时用warps()函数来解决该问题

from functools import wraps
 
def a_new_decorator(a_func):
    @wraps(a_func)
    def wrapTheFunction():
        print("I am doing some boring work before executing a_func()")
        a_func()
        print("I am doing some boring work after executing a_func()")
    return wrapTheFunction
 
@a_new_decorator
def a_function_requiring_decoration():
    """Hey yo! Decorate me!"""
    print("I am the function which needs some decoration to "
          "remove my foul smell")
 
print(a_function_requiring_decoration.__name__)
# Output: a_function_requiring_decoration

四，使用蓝本

from functools import wraps
def decorator_name(f):
    @wraps(f)
    def decorated(*args, **kwargs):
        if not can_run:
            return "Function will not run"
        return f(*args, **kwargs)
    return decorated
 
@decorator_name
def func():
    return("Function is running")
 
can_run = True
print(func())
# Output: Function is running
 
can_run = False
print(func())
# Output: Function will not run