python : How to check if input is not equal to any item in a 2d array?

Question

我试图检查输入的用户名是否等于列表中项目的第二个索引，并且我尝试使用!=，但它仍然让相同的用户名被注册。代码有什么问题？

注册用户名:

user_list = [['usr1','Daniel'],['usr2','Raymond'],['usr3','Emanuel']]

name = input("Please enter your name : ")
while True:
     if name == '':
          name = input("Please enter your name : ")
     else:
          for user in user_list:
               if name != user[1]:
                    break # break out for loop
          else:
               print("This username has been registered")
               name = input("Please try another username : ") 
               continue # continue the while loop
          break # break out while loop
print("Username registered as",name)

编辑:

!= 和 == 的结果似乎不同，== 有效。

登录用户名:

user_list = [['std1','Daniel'],['std2','Raymond'],['std3','Emanuel']]

name = input("Please enter your name : ")
while True:
     if name == '':
          name = input("Please enter your name : ")
     else:
          for user in user_list:
               if name == user[1]:
                    break # break out for loop
          else:
               print("Unregistered username")
               name = input("Please try another username : ") 
               continue # continue the while loop
          break # break out while loop
print("Logged in as",name)

Answer 1

你已经非常接近了!
您想要做什么:如果 user_list 中有任何名称与新名称匹配，则跳出循环。
它当前正在做什么:如果 user_list 中有任何名称与新名称不匹配，则跳出循环。
也就是说，如果你输入 Daniel，因为 Daniel != Raymond，你就会提前休息。

相反，如果新输入的名称不存在于名称列表中，您应该做的是中断:

user_list = [['usr1','Daniel'],['usr2','Raymond'],['usr3','Emanuel']]

name = input("Please enter your name : ")
while True:
    if name == '':
         name = input("Please enter your name : ")
    else:
        if name in [user[1] for user in user_list]:  # existing names list
            print("This username has been registered")
            name = input("Please try another username : ")
        else:
            break
print("Username registered as",name)