Day 12 闭包函数/装饰器

闭包函数

闭包函数:将函数和变量包起来

def make_averager():
    series = []

    def averager(new_value):
        series.append(new_value)
        total = sum(series)
        return total/len(series)
    return averager

avg = make_averager()
print(avg(10))
print(avg(20))
print(avg(30))

10.0
15.0
30.0

装饰器

装饰器也是一个函数

两大原则:

1. 不改变被装饰函数的源代码
2. 不改变被装饰函数的调用

def deco(func):
    def wrapper(*args, **kwargs):
        res = func(*args, **kwargs)
        print("I'm Tiny")
        return res

    return wrapper


@deco
def say(x):
    print(f'Hello,{x}')
    return 'Nice to meet you'


say = say('nick')
print(say)

上述的装饰器,最后调用say()的时候,其实是在调用wrapper(),如果say()有返回值,那么wrapper()内也需要返回这个值,即上述的res

如果say()需要传入参数,那么wrapper()内也要传入相同的参数,但是因为我们不知道say()中传入什么参数,所有可以使用*args,**kwargs万能参数来表示

python装饰器语法糖

在被装饰函数正上方，并且是单独一行写上@装饰器名

就可以直接调用被装饰函数

三层装饰器

import time

current_uesr = {'username': None}


def auth(engine='file'):

    def login(func):
        # func = 最原始的index
        def wrapper(*args, **kwargs):

            if current_user['username']:
                res = func(*args, **kwargs)

                return res

            user = input('username: ').strip()
            pwd = input('password: ').strip()

            if engine == 'file':
                print('base of file')
                if user == 'nick' and pwd == '123':
                    print('login successful')
                    current_uesr['usre'] = user
                    res = func(*args, **kwargs)

                    return res
                else:
                    print('user or password error')
            elif engine == 'mysql':
                print('base of mysql, please base of file')
            elif engine == 'mongodb':
                print('base of mongodb, please base of file')
            else:
                print('please base of file')

        return wrapper

    return login


@auth(engine='mysql')
def home(name):
    print(f"welcome {name} to home page")
    time.sleep(1)


@auth(engine='file')
def index():
    print('welcome to index')
    time.sleep(1)


res = index()

username: nick
password: 123
base of file
login successful
welcome to index