Python学习笔记（十）：

装饰器的应用
列表生成式
生成器
迭代器
模块：time,random

1. 装饰器的应用-登陆练习

login_status = False	# 定义登陆状态

def type(auth_type):	# 装饰器传参函数

    def login(fucn):	# 装饰器函数

        def inner():	# 附加功能

            global login_status		# 将登陆状态变量变为全局变量

            if login_status == False:

                if auth_type == 'jingdong':

                    username = input('username:')

                    password = input('password:')

                    with open('jingdong.txt','r') as f:

                        lines = f.readlines()

                        for i in lines:

                            i = eval(i)

                            if username in i and password == i[username]:

                                print('welcome %s' % (username))

                                login_status = True

                                fucn()

                            else:

                                print('wrong username or password')

                elif auth_type == 'weixin':

                    username = input('username:')

                    password = input('password:')

                    with open('weixin.txt', 'r') as f:

                        lines = f.readlines()

                        for i in lines:

                            i = eval(i)

                            if username in i and password == i[username]:

                                print('welcome %s' % (username))

                                login_status = True

                                fucn()

                            else:

                                print('wrong username or password')

            else:

                pass

        return inner

    return login

@type('jingdong')	# 连接装饰器

def home():			# 功能函数

    print('welcome to home page')

@type('weixin')

def finance():

    print('welcome to finance page')

@type('jingdong')

def book():

    print('welcome to book page')

if __name__ == '__main__':

    while True:

        print('welcome to JD:')

        print('choice 1 to home')

        print('choice 2 to finance')

        print('choice 3 to book')

        print('choice 0 to back')

        choice = input('Where are you going:')

        if choice == '1':

            home()

        elif choice == '2':

            finance()

        elif choice == '3':

            book()

        elif choice == '0':

            break

2. 列表生成式

代码示例：

a = [x for x in range(10)]

print(a)	# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

a = [x*2 for x in range(10)]

print(a)	# [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]

def f(n):

    return n**3

a = [f(x) for x in range(10)]

print(a)	# [0, 1, 8, 27, 64, 125, 216, 343, 512, 729]

3. 生成器

代码示例：

# 第一种方法

s = (x for x in range(100))	# 生成器

# for的作用：消除内存占用，判断遍历完成

for i in s:

	print(i)

# 第二种方法

def foo():

    i = range(22)

    yield i

for i in foo():

    print(i)

# send方法给yield赋值

def bar():

    print('ok1')

    count = yield 1 # 接收'ee'

    print(count)

    print('ok2')

    yield 2

b = bar()

b.send(None)	# 相当于next(b)

b.send('ee')	# 将'ee'赋值给第一个yield

4. 迭代器

生成器都是迭代器

什么是迭代器？

有iter方法
有next方法

5. 模块

1. time模块

函数/方法：

time() -- return current time in seconds since the Epoch as a float

clock() -- return CPU time since process start as a float

sleep() -- delay for a number of seconds given as a float

gmtime() -- convert seconds since Epoch to UTC tuple

localtime() -- convert seconds since Epoch to local time tuple

asctime() -- convert time tuple to string

ctime() -- convert time in seconds to string

mktime() -- convert local time tuple to seconds since Epoch

strftime() -- convert time tuple to string according to format specification

strptime() -- parse string to time tuple according to format specification

tzset() -- change the local timezone

代码示例：

print(time.strftime('%Y-%m-%d  %H:%M:%S'))	#2017-09-20  13:44:01

print(time.strptime('2017-09-20  12:53:21','%Y-%m-%d  %H:%M:%S'))

# time.struct_time(tm_year=2017, tm_mon=9, tm_mday=20, tm_hour=12, tm_min=53, tm_sec=21, tm_wday=2, tm_yday=263, tm_isdst=-1)

2. random模块

print(random.randint(1,8))		# 从1-8中随机取值

print(random.choice('hello'))	# 从‘hello’中随机取一个字母

# 实现验证码

def v_code():

    code = ''

    for i in range(5):

        add = random.choice([random.randrange(10),chr(random.randrange(65,91))])

        code += str(add)

    print(code)

v_code()