Python Learning-A few simple small programs

1, Output 1 to 100 of even

#!/usr/bin/env python#-*-coding:utf-8-*-#定义初始值start =1while True: #判断start的值若其为51, the last time you have output 100, jump out of the loop   if start= =51:     break   print start*2   start +=1

　

2, Output 1 to 100 of the odd

#!/usr/bin/env python#-*-coding:utf-8-*-#定义初始值start =1while True:   if start==100:     break   #% operation is take remainder   if start%2 ==1:     print start   start +=1

3, the output 1-2+3-4+...+99-100 and

The main idea is to judge the sign in front of start--using conditional statements to determine whether it is odd or even

the symbol before the variable	Odd	even
Start	1	-1

Code implementation:

#!/usr/bin/env python#-*-coding:utf-8-*-#定义初始值, sum refers to the sum, and start refers to an integer of 1-100 sum=0start=1while True:   if start==101 : The break   #% operation takes the remainder, judging whether it is odd or even   if start%2 ==1:     sum=sum+start    if start%2 ==0:     sum=sum-start   

4, user login three times retry

The main implementations are:

• Set the initial user name and login password;
• Enter the login page to remind the user to enter user name and password;
• If the user name is wrong, re-input, if the user login password three times to start again enter the user name and user login password;

Code implementation:

#!/usr/bin/env python#-*-coding:utf-8-*-#先设定初始用户名和登录密码init_usrname =raw_input (' Please enter initial username: ') init _password=raw_input (' Please enter initial password: ') #打印输出设置好的用户名和初始登录密码print (init_usrname) print (Init_password) # Enter login to meet, flag0 refers to the number of errors entered password #flag1 refers to the login success flag bit flag0=0flag1=0print (' >>>user login<<< ') while true:# Prompt user to enter user name Usr=raw_input (' Enter username: ') if Usr==init_usrname: #输入用户名正确则进入到输入登录密码阶段 #判断输错登录密码次数 W Hile flag0<3:password=raw_input (' Enter password: ') if Password==init_password: #若密码输入                Correct login Success thus jumping out of loop print (' Success login! ') Flag1=1 break Else: #计算输错次数, flag plus one flag0 +=1 if f per error    Lag0<=2:print (' Wrong password,enter again! ') #输错三次跳出输入登录密码环节重新进行用户名的输入, the corresponding flag will also be zeroed if Flag1==1:break flag0=0 print (' You have tried t    Hree times,login again! ') Else        Print (' Wrong username,enter again! ') 

　

Timing Effect:

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Python Learning-A few simple small programs