【Python3】条件语句与循环语句

python基础

浏览数:132

2019-4-27

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1 条件语句

  • 例1:
if 条件:
    ...
else:
    ...
  • 应用
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

username = input("请输入用户名:")
password = input("请输入密码:")


if username  == 'fcc' and password == '123':
    print("欢迎登陆!")
else:
    print("用户名或密码错误!")
  • 例2:
if 条件:
    ...
elif 条件:
    ...
else:
    ...   
  • 应用:
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

sex = input("请输入你的性别:")

if sex == "男":
    print("傻x,自己性别都忘了!")
elif sex == "女":
    print("...你在想想,你忘了你已经做了手术了吗...")
else:
    print("人妖.......")

2 循环语句

  • while
while 条件:
    continue # 开始下一次循环
    break # 跳出所有循环
  • 例:
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

i = 0
while i < 3:
    username = input("请输入用户名:")
    password = input("请输入密码:")
    if username == 'fcc' and password == '123':
        print("欢迎登陆!")
        break
    else:
        print('用户名或密码错误')
        i += 1

3 练习

    1. 使用while循环输入 1 2 3 4 5 6 8 9 10
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

i = 1
while True:
    if i == 7:
        i += 1
        continue
    print(i)
    i += 1
    if i == 11:
        break
    1. 求1-100的所有数的和
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

value = 0
i = 1
while i < 101:
    value = value + i
    i += 1
print(value)
    1. 输出 1-100 内的所有奇数
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

i = 1

while i < 101:
    if i % 2 == 1:
        print(i)
    i += 1
    1. 输出 1-100 内的所有偶数
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

i = 1

while i < 101:
    if i % 2 == 0:
        print(i)
    i += 1
    1. 求1-2+3-4+5 … 99的所有数的和
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

value = 0
i = 1

while i < 100:
    if i % 2 == 1:
        value = value + i
        i += 1
    elif i % 2 == 0:
        value = value - i
        i +=1
print(value)
    1. 用户登陆(三次机会重试)
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Author:Chuncheng.Fan <xmzncc@gmail.com>

i = 0

while i < 3:
    username = input("请输入用户名:")
    password = input("请输入密码:")
    if username == 'fcc' and password == '123':
        print("欢迎登陆!")
        break
    else:
        print("用户名或密码错误")
        i += 1

作者:Carson