装饰器

装饰器

新增加了一个额外的功能

装饰器本质就是一个 给函数增加功能的函数

增加功能需要注意一下两点：

1. 不改变原函数的源代码
2. 不改变原函数的调用方式

案例

# v1
import time

def index():
    """被装饰的函数"""
    print('index')
    time.sleep(1)

# time_count装饰器：对被装饰函数计时
def time_count(func):  # func才是真正的index
    """装饰器"""

    def wrapper():
        start = time.time()
        func()
        end = time.time()
        print(end - start)

    return wrapper


index = time_count(index)  # index == wrapper
index()  # wrapper()

# v2:带返回值

import time


def index():
    """被装饰的函数"""
    print('x',x)
    print('index')
    time.sleep(1)

    return 'index'


# time_count装饰器：对被装饰函数计时
def time_count(func):  # func才是真正的index
    """装饰器"""

    def wrapper():
        start = time.time()
        res = func()  # index()
        end = time.time()
        print(end - start)

        return res

    return wrapper


index = time_count(index)  # index == wrapper
res = index()  # wrapper()
print(res)

# v3：加参数

import time


def index(x,y,z=10):
    """被装饰的函数"""
    print('x',x)
    print('index')
    time.sleep(1)

    return 'index'


# time_count装饰器：对被装饰函数计时
def time_count(func):  # func才是真正的index
    """装饰器"""

    def wrapper(*args,**kwargs):  # (10, 20)  # *args和**kwargs接收了所有的参数
        start = time.time()
        res = func(*args,**kwargs)  # index()  # *(10,20)  # *args和**kwargs打散参数传给真正的index
        end = time.time()
        print(end - start)

        return res

    return wrapper


index = time_count(index)  # index == wrapper
res = index(10,20,320)  # wrapper()
print(res)

登录装饰器

#装饰器模板
def deco(func):
    def wrapper(*args,**kwargs):
        res = func(*args,**kwargs)
        return res
    return wrapper

二层装饰器：# 1. 用来装饰函数的，它本质是函数# 2. 不改变函数源代码# 3. 不改变函数调用方式

# python装饰器语法糖（就是让代码更简洁）
username_list = []


def login_deco(func):
    def wrapper(*args, **kwargs):

        if username_list:
            print('已经登录，请勿重复登录')
            res = func(*args, **kwargs)
            return res

        username_inp = input('请输入用户名：')
        pwd_inp = input('请输入密码：')

        with open('user_info.txt', 'r', encoding='utf8') as fr:
            for user_info in fr:
                username, pwd = user_info.strip().split(':')
                if username_inp == username and pwd_inp == pwd:
                    print('登录成功')
                    username_list.append(username)

                    res = func(*args, **kwargs)
                    return res

            else:
                print('登录失败')

    return wrapper

@login_deco  # index = login_deco(index)
def index(x, y):
    print('index')
    print('x,y', x, y)

    return 123

res = index(10, 20)

三层装饰器

username_list = []


def sanceng(role):
    def login_deco(func):
        def wrapper(*args, **kwargs):

            if username_list:
                print('已经登录，请勿重复登录')
                res = func(*args, **kwargs)
                return res

            username_inp = input('请输入用户名：')
            pwd_inp = input('请输入密码：')

            with open(f'{role}_info.txt', 'r', encoding='utf8') as fr:
                for user_info in fr:
                    username, pwd = user_info.strip().split(':')
                    if username_inp == username and pwd_inp == pwd:
                        print('登录成功')
                        username_list.append(username)

                        res = func(*args, **kwargs)
                        return res

                else:
                    print('登录失败')

        return wrapper

    return login_deco


@sanceng('user')
def index(x, y):
    print('index')
    print('x,y', x, y)

    return 123


res = index(10, 20)