Python day 12

Closure function

Closed (closed function internal functions) package (comprising): a function of an external reference to an internal function rather than global scope scope.

Two kinds of methods as a function of parameter passing

Use parameters
```
def func(x):
    print(x)

func(1)
```

Contracted function

def func(x):
#    x = 1
    def f1():
        print(x)
    return f1

f2 = func(2)

Decorator

No reference decorator

What is the decorator

The decorator is a function of nature, decorator is to add additional functionality to be decorative objects

Pay attention to two things:

Decorator function object itself can be called any
Objects can also be decorated with any function callable objects

Achieve decorator must follow two principles

1. 不修改被装饰对象的源代码
2. 不修改被装饰对象的调用方式

Decorator usage

import time

def index():
    print('welcome to index')
    time.sleep(1)
    
    return 123

def home(name):
    print(f'welcome {name} to page')
    time.sleep(1)
    
    return name

def time_count(func):
    #func = 最原始的index
    def wrapper(*args,**kwargs):
        start = time.time()
        res = func(*args,**kwargs)
        end = time.time()
        print(f'{func} time is {start - end}')
        
        return res
    return wrapper

home = time_count(home)
home('simple')

index = time_count(index)
index()

Decorator syntax sugar

#在被装饰函数上面单独写上@装饰器名
@time_count
# @time_count 就等于 home = time_count(home)
def home(name):
    print(f'welcome {name} to page')
    time.sleep(1)
    
    return name

Decorative template

def deco(func):
    def wrapper(*args,**kwargs):
        res = func(*args,**kwargs)
        return res
    return wrapper

There are parameters decorator

#三层函数
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('admin')
def index(x, y):
    print('index')
    print('x,y', x, y)
    return 123

res = index(10, 20)

Blog finishing day12