20170417if.else条件判断和多条件判断

1.条件判断

即：如果条件成立，就......；反之，就.......　　

def account_login():#定义函数，不需要参数
    password = input('Password:')#用input获得用户输入的字符串并储存在变量password中
    if password =='12345':
        print('Login success!')#设置条件
    else:
        print('Wrong password or invalid input!')
        account_login()#输入错误情况时，再次调用函数
account_login()#调用函数

当if后的表达式过长时，可以采取给变量赋值的办法

password_correct = password == '12345'

if password_correct: #此时password_correct的值为1/0

#判断学生成绩

while True:
    grade = int(input('请输入你的分数'))
    if 100 >= grade >= 90:
        print('A')
    elif 90 > grade >= 80:
        print('B')
    elif 80 > grade >= 70:
        print('C')
    elif 70 > grade >= 60:
        print('D')
    elif grade < 0 or grade > 100:
        print('输入错误')
    else:
        print('E')

2.多条件判断

password_list = ['*','12345']
def account_login():
    password = input('Password:')
    password_correct = password == password_list[-1]
    password_reset = password == password_list[0]
    if password_correct:
        print('Login success!')
    elif password_reset:
        new_password = input('Enter a new password:')
        password_list.append(new_password)
        print('Your password has changed successfully!')
        account_login()
    else:
        print('Wrong password or invalid input!')
        account_login()
account_login()