Python-流程控制之循环

# 1. while循环：条件循环# I:基本语法# while 条件：#     代码1#     代码2#     代码3#     ...# 示范# name_of_bk='huangdong'# paw_of_bk='123'## tag=True# while tag:#     inp_name=input('your name>>:')#     inp_pwd=input('your password>>:')#     if inp_name == name_of_bk and inp_pwd == paw_of_bk:#         print('login successful')#         tag=False#     else:#         print('username or password error')##     print('emmmmmm')# II: while+break:break表明结束本层循环# 示范：# while True:#     print(1)#     break#     print(2)#     print(3)# name_of_bk='huangdong'# paw_of_bk='123'## while True:#     inp_name=input('your name>>:')#     inp_pwd=input('your password>>:')#     if inp_name == name_of_bk and inp_pwd == paw_of_bk:#         print('login successful')#         break#     else:#         print('username or password error')##     print('emmmmmm')# III: while + continue: continue表明结束本次循环，直接进入下一次# 示范# count=1# while count <6:#     if count == 3:#         count+=1#         continue#     print(count)#     count+1# 输错三次退出# name_of_bk='huangdong'# paw_of_bk='123'## count=0# while True:#     if count == 3:#         print('输错次数过多..')#         break#     inp_name=input('your name>>:')#     inp_pwd=input('your password>>:')#     if inp_name == name_of_bk and inp_pwd == paw_of_bk:#         print('login successful')#         break#     else:#         print('username or password error')#         count+=1 #count=3 输错3次###     print('emmmmmm')# IV:while + else# count=0# while True:#     if count == 10:#         break#     print(count)#     count+=1# else:#     print('else的子代码块只有在while循坏没有被break打断的状况下才会执行')# count=0# while count <= 10:#     print(count)#     count+=1## else:#     print('else的子代码块只有在while循坏没有被break打断的状况下才会执行')name_of_bk='huangdong'pwd_of_bk='123'count=0tag=Truewhile tag:    if count == 3:        print('输错次数过多...')        break    inp_name=input('your name>>:')    inp_paw=input('your password>>:')    if inp_name == name_of_bk and inp_paw == inp_paw:        print('login password')        while tag:            print('''            0 退出            1 购物            2 支付            3 查看购物车            ''')            cmd=input('>>:')            if cmd == '0':                tag=False                continue            if cmd == '1':                print('购物...')            elif cmd =='2':                print('支付..')            elif cmd == '3':                print('购物车')            else:                print('输入错误的指令')    else:        print('username or password error')