题解 | #禁止重复注册#

current_users = ['Niuniu','Niumei','GURR','LOLO']
new_users = ['GurR','Niu Ke Le','LoLo','Tuo Rui Chi']
for i in new_users:
    flag = False
    for j in current_users:
        if i.lower() == j.lower():
            flag = True 
    if flag:
        print(f'The user name {i} has already been registered! Please change it and try again!')
    else:
        print(f'Congratulations, the user name {i} is available!')
		
要先判断完内循环对错，再输出，所有用一个局部变量存储
若先若每一个内循环都比较了就打印，则会出现很多多余语句，比如GurR与Niuniu对比，就会马上print