if判断的流程控制

if判断的流程控制

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　　if语句可以根据用户的输入内容或获取的数据进行条件判断，以响应对应条件的代码块。

　　语法：if...else...

　　例子：

username = input("username:")
password = input("password:")
if username == "george" and password == "georgeNB":
    print("Welcome My Lord")
else:
    print('Wrong username or password！')

　　语法：if...elif...else  用于多条件判断。

　　例子一：

age = 56
while True:
    user_age = int(input('input your age:'))
    if user_age > age:
        print('try smaller')
    elif user_age < age:
        print('try big')
    else:
        user_age = "exit"
        print('your got it!')
        break

　　例子二：

while True:
    score = int(input("input your score:"))
    if score == 100:
        print("your score 'A++'")
    elif 90 <= score <=95:
        print("your score 'A+' ")
    elif 80 <= score <= 89:
        print("your score 'A'")
    elif 70 <= score <=79:
        print("your score 'B+'")
    elif 60 <= score <=69:
        print("your score 'B'")
    elif score <=59:
        print("your score 'C'")
    else:
        score > 100
        print("Wrong data!")
        break

　　# # # 作业 # # #

　　# 1、猜年龄，猜三次

age = 56
count = 0
while True:
    user_age = int(input('input your age:'))
    if user_age > age:
        count += 1
        print(count)
        print('try smaller')
        if count >2:
            break
    elif user_age < age:
        count += 1
        print(count)
        print('try big')
        if count >2:
            break
    else:
        user_age = age
        print('your got it!')
        break

　　# 2、猜年龄，每隔三次问一次，是否继续(Y/N)

age = 56
count = 0
while True:
    user_age = int(input('input your age:'))
    if user_age > age:
        count += 1
        print(count)
        print('try smaller')
        if count >2:
            print("Do you want to choose to try again(Y/N)")
            choose = input("input your choose:")
            if choose == "Y" or "y":
                count =0
            else:
                break
    elif user_age < age:
        count += 1
        print(count)
        print('try big')
        if count >2:
            print("Do you want to choose to try again(Y/N)")
            choose = input("input your choose:")
            if choose == "Y" or "y":
                count = 0
            else:
                break
    else:
        user_age = age
        print('your got it!')
        break

　　# 3、三次登录(残缺版1.0beta)

username = "george"
password = "123"
count =0

while True:
    input_username = input("input your username:")
    input_password = input("input your password:")
    if username == input_username and password == input_password:
        print("Welconme My Lord!")
        break
    else:
        count +=1
        print("Your username or password is Wrong!")
        if count>2:
            print("Your username or passwrod is Wrong three times, It is lock")
            break

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