函数式编程：用户登录和注册

#!/usr/bin/env python
# -*- coding:utf-8 -*-
##第一种方法,面向过程
'''
user = input("请输入用户名：")
paw = input("请输入密码：")

f = open('db','r',encoding='utf-8')
for line in f:
    line=line.strip()
    line_list=line.split("$")


    if user==line_list[0] and paw ==line_list[1]:
        print("登录成功")
        break
'''

#第二种方法，函数式编程
def login(user,paw):
    """
    登录
    :param user:
    :param paw:
    :return:
    """
    f = open('db', 'r', encoding='utf-8')
    for line in f:
        line = line.strip()
        line_list = line.split("$")

        if user == line_list[0] and paw == line_list[1]:
           # print("登录成功")
            return True
    return False

def register(user,paw):
    """
    注册，已经有的用户名不能重复注册
    注册，打开文件，在后面追加 a
    用户名$密码
    :param user:
    :param paw:
    :return: 注册成功
    """
    with open('db', 'a', encoding='utf-8') as f:
        temp = "\n"+user+"$"+paw
        f.write(temp)


    return True

def user_exist(user):
    """
    用户名是否已经存在
    一行一行查找，用户名存在，True
    :return:
    """
    with open('db','r',encoding='utf-8') as f:
        for line in f:
            line = line.strip()
            line_list = line.split("$")
            if line_list[0] == user:
                return True

    return False


print("欢迎登录自学系统")
inp =input("输入1：登录；输入2：注册")
if inp=="1":
    user = input("请输入用户名：")
    paw = input("请输入密码：")

    is_login = login(user, paw)
    if is_login == True:
        print("登录成功")
    else:
        print("登录失败")

elif inp=="2":
    user = input("请输入用户名")
    paw = input("请输入密码：")
    is_exist = user_exist(user)
    if is_exist:
        print("用户名已经存在，无法注册")
    else:
        result = register(user,paw)
        if result:
            print("注册成功")
        else:
            print("注册失败")