小白的Python之路 day1 表达式if ... else ,while循环,for循环

表达式if ... else

一、用户登陆验证

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# 提示输入用户名和密码
  
# 验证用户名和密码
#     如果错误,则输出用户名或密码错误
#     如果成功,则输出 欢迎,XXX!
 
 
#!/usr/bin/env python
# -*- coding: encoding -*-
  
_username = 'qian'
_password = 'zxc123'
username = input("username:")
password = input("password:")
if _username == username and _password == password:
    print("Welcome user {name} login...".format(name=username))
else:
    print("Invalid username or password!")
 

二、猜年龄游戏

在程序里设定好你的年龄,然后启动程序让用户猜测,用户输入后,根据他的输入提示用户输入的是否正确,如果错误,提示是猜大了还是小了,

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
my_age = 26
 
guess_age = int(input("guess age:") )
if guess_age == my_age :
  print("yes, you got it. ")
elif guess_age > my_age:
  print("think smaller...")
else:
  print("think bigger!")
 

二、while loop   

 有一种循环叫死循环

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count = 0
while True:
    print("死循环",count)
    count +=1
    

上面猜年龄用while 循环去实现:  只猜3次

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
count = 0
 
my_age = 26
 
while count < 3:
    guess_age = int(input("guess age:") )
    if guess_age == my_age :
        print("yes, you got it. ")
        break
    elif guess_age > my_age:
        print("think smaller...")
    else:
        print("think bigger!")
    count +=1
else:
    print("you have tried too many times..fuck off")

     

 

 

三、表达式for loop

最简单的循环5次

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#_*_coding:utf-8_*_
__author__ = 'Many Qian'
 
 
for in range(5):
    print("loop:", i )

输出:

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loop: 0
loop: 1
loop: 2
loop: 3
loop: 4
 

需求一:还是上面的程序,但是遇到小于5的循环次数就不走了,直接跳入下一次循环

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for in range(10):
    if i<5:
        continue #不往下走了,直接进入下一次loop
    print("loop:", i )

需求二:还是上面的程序,但是遇到大于5的循环次数就不走了,直接退出

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for in range(10):
    if i>5:
        break #不往下走了,直接跳出整个loop
    print("loop:", i )

用上面学的for循环做猜年龄:

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
 
my_age = 26
for i in range(3):
    guess_age = int(input("guess age:") )
    if guess_age == my_age :
        print("yes, you got it. ")
        break
    elif guess_age > my_age:
        print("think smaller...")
    else:
        print("think bigger!")
else:
    print("you have tried too many times..fuck off")
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