Python循环

# 循环loop #

    有限循环 ，次数限制
    无限循环=死循环
    continue 结束本次循环，继续下一次循环
    break 跳出整个当前的循环

# for循环 #

## 实例1： ##
    #基本语法 
    for i in range(100):
        print(i)
    #range(起始位,参数,步长)
    for j in range(1,100,2):#包括1，不包括100，顾头不顾尾
        print(j)



## 实例2： ##
    #用户只能输入3次：
    name = 'ccy'
    passwd = '123456'

    for i in range(3):
        username = input("Username:")
        password = input("Password:")
        if  name==username and passwd==password:
            print("welcome %s login" %(username))
            break
        else:
            print("输入错误")
## 实例3： ##
    #列表遍历，enumerate（枚举），遍历加上序号，前面可以接受多个参数：
    a=['wuchao','jinxin','xiaohu','sanpang','ligang']
    for i,v in enumerate(a,1):#enumerate（枚举）遍历时加上序号，可以自定义起始位置，for循环后面可以跟列表、字典、元组等，前面可以用2个参数接收
    print(i,v)

# while循环 #

## 实例1： ##
    #用户只能输入3次：
    name = 'ccy'
    passwd = '123456'
    conut = 0
    while conut<3:
        username = input("Username:")
        password = input("Password:")
        if  name==username and passwd==password:
            print("welcome %s login" %(username))
            break
        else:
            print("输入错误")
        conut+=1



## 实例2： ##
    #加判断，3次输入结束，确认是否继续
    name = 'ccy'
    passwd = '123456'
    count = 0
    while count<3:
        username = input("Username:")
        password = input("Password:")
        if  name==username and passwd==password:
            print("welcome %s login" %(username))
            break
        else:
            print("输入错误")
        count+=1
        if count ==3:
            keep_going = input("还想玩么?[y/n]")
            if keep_going == 'y':
                count = 0
    else:
        print('结束了')


# break #
    跳出当前循环，循环结束，while和for循环后面都可以接else,如果程序正常结束，则走else，如果被break中断，则不走else
    #while......else.....
    while count <1:
        print(count)
        break
    else:
        print("111")
    
    #for......else.....
    for i in range(3):
        print(count)
        break
    else:
        print("111")


# continue #
    跳出本次循环,开始下一次循环

# for循环 #
## 实例1： ##
    #基本语法 
    for i in range(100):
        print(i)
    #range(起始位,参数,步长)
    for j in range(1,100,2):#包括1，不包括100，顾头不顾尾
        print(j)

## 实例2： ##
    #用户只能输入3次：
    name = 'ccy'
    passwd = '123456'

    for i in range(3):
        username = input("Username:")
        password = input("Password:")
        if  name==username and passwd==password:
            print("welcome %s login" %(username))
            break
        else:
            print("输入错误")
## 实例3： ##
    #列表遍历，enumerate（枚举），遍历加上序号，前面可以接受多个参数：
    a=['wuchao','jinxin','xiaohu','sanpang','ligang']
    for i,v in enumerate(a,1):#enumerate（枚举）遍历时加上序号，可以自定义起始位置，for循环后面可以跟列表、字典、元组等，前面可以用2个参数接收
    print(i,v)

# while循环 #
## 实例1： ##
    #用户只能输入3次：
    name = 'ccy'
    passwd = '123456'
    conut = 0
    while conut<3:
        username = input("Username:")
        password = input("Password:")
        if  name==username and passwd==password:
            print("welcome %s login" %(username))
            break
        else:
            print("输入错误")
        conut+=1

## 实例2： ##
    #加判断，3次输入结束，确认是否继续
    name = 'ccy'
    passwd = '123456'
    count = 0
    while count<3:
        username = input("Username:")
        password = input("Password:")
        if  name==username and passwd==password:
            print("welcome %s login" %(username))
            break
        else:
            print("输入错误")
        count+=1
        if count ==3:
            keep_going = input("还想玩么?[y/n]")
            if keep_going == 'y':
                count = 0
    else:
        print('结束了')


# break #
    跳出当前循环，循环结束，while和for循环后面都可以接else,如果程序正常结束，则走else，如果被break中断，则不走else
    #while......else.....
    while count <1:
        print(count)
        break
    else:
        print("111")
    
    #for......else.....
    for i in range(3):
        print(count)
        break
    else:
        print("111")


# continue #
    跳出本次循环,开始下一次循环