day18

1、编写课上讲解的有参装饰器准备明天默写

from functools import wraps
def auth(db_type):
    @wraps
  	def deco(func):
        def wrapper(*args, **kwargs):
        		name = input('请输入用户名：').strip()
            password= input('请输入密码：').strip()
            if db_type == 'file':
              	print('基于文件的验证！')
                if name == 'egon' and password == '123':
          					res = func(*args, **kwargs)
                    return res
            elif db_type == 'mysql':
              	print('基于 mysql 的验证')
            elif db_type == 'ldap':
              	print('基于 ldap 的验证')
            else:
              	print('不支持该db_type')
        return wrapper
    return deco
          
@auth('file')
def index(x,y):
  	print('index-->%s,%s'%(x,y))
    
@auth('mysql')
def home(name):
  	print('home-->%s'%name)
    
@auth('ldap')
def transfer():
  	print('transfer')
    
index（1，2）
home('egon')
transfer()


结果展示：
index-->1,2
home-->egon
transfer

2：还记得我们用函数对象的概念，制作一个函数字典的操作吗，来来来，我们有更高大上的做法，在文件开头声明一个空字典，然后在每个函数前加上装饰器，完成自动添加到字典的操作

func_dic = {}
count = 0
def outter(func):
    def wrapper(*args, **kwargs):
        global count
        count += 1
        res = func(*args, **kwargs)
        if func.__name__ not in func_dic.values():
            func_dic[f'{count}'] = func.__name__

        return res
    return wrapper

@outter
def login():
    print('login...')


@outter
def check_balance():
    print('check_balance...')


@outter
def withdraw():
    print('withdraw...')

login()
check_balance()
withdraw()
login()
print(func_dic)

3、 编写日志装饰器，实现功能如：一旦函数f1执行，则将消息2017-07-21 11:12:11 f1 run写入到日志文件中，日志文件路径可以指定
注意：时间格式的获取
import time
time.strftime('%Y-%m-%d %X')

import time
from functools import wraps

def tail_log(path):
    def outter(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            current_time = time.strftime('%Y-%m-%d %X')
            with open(path, 'a', encoding='utf-8')as f:
                f.write(f'{current_time} {func.__name__} run
')
            res = func(*args, **kwargs)
            return res
        return wrapper
    return outter


@tail_log(path='access.log')
def f1():
    print('f1正在执行...')

f1()

结果展示：
2020-03-24 16:14:41 f1 run

4、基于迭代器的方式，用while循环迭代取值字符串、列表、元组、字典、集合、文件对象

def run(obj):
    obj_iterator = obj.__iter__()
    while True:
        try:
            print(next(obj_iterator), end=' ')
        except StopIteration:
            break


str_obj = 'hello'
list_obj = [1, 2, 3, 4]
tuple_obj = (5, 6, 7, 8)
dic_obj = {'name': 'egon', 'age': 18}
set_obj = {10, 11, 12, 13}

run(str_obj) #h e l l o
run(list_obj) #1 2 3 4
run(tuple_obj) #5 6 7 8
run(dic_obj) #name age
run(set_obj) #10 11 12 13

with open('a.txt', 'r', encoding='utf-8')as f:
    run(f) 
   
'''
111
222
333
'''

5、自定义迭代器实现range功能

def my_range(start, stop, step=2):
    while start < stop:
        yield start
        start += step

g = my_range(0,5)
print(g)
res = next(g)
print(res) #0
res = next(g)
print(res) #2
res = next(g)
print(res) #4
res = next(g)
print(res) #抛出异常