如果 x 在 [list] 迭代器中

Question

def new_user() -> str:
    users = []
    print("Welcome to The 'Create New User' Interface")
    sleep(0.5)
    x = input("Enter Name to Use for Account Access\n*Name is Case Sensitive to Access Account*: ")
    if x in users:
        x = input("That User Already Exists! Enter a New Name: ")
        users.append(x)
        print("Your Account Access Name is: " + str(x))
    else:
        users.append(x)
        print("Your Account Access Name is: " + str(x))

所以我不知道如何表达这个问题，但我有这段代码，如您所见，我想检查用户输入的名称是否已经存在，如果存在，它将提示输入新名称并将其添加到列表中，如果它不存在，它会将其添加到列表中，但是有一种解决方法，如果列表已经包含名称并且用户输入了相同的名称 if x in users:代码将运行，当提示输入另一个名称时，如果他们输入相同的名称，它不会识别它已经存在并将其添加到列表中，我该如何防止这种情况发生？

Answer 1

要获得有效的用户输入，请将请求包装在一个循环中，并且当您有有效输入 break 时，例如：

print("Enter Name to Use for Account Access")
print("*Name is Case Sensitive to Access Account*")
while True:
    x = input("Enter a Name: ")
    if x not in users:  # Valid input
        break
    print("That User Already Exists!")

users.append(x)
print("Your Account Access Name is:", x)

Answer 2

解决方案

users = []
print("Welcome to The 'Create New User' Interface")
x = input("Enter Name to Use for Account Access\n*Name is Case Sensitive to Access Account*: ")
while x in users:
    x = input("That User Already Exists! Enter a New Name: ")
users.append(x)
print("Your Account Access Name is: " + str(x))

只需将您的 if 循环更改为 while 循环，该循环将一直持续到给出唯一名称为止。

建议

users = []
print("Welcome to The 'Create New User' Interface")
while True:
    user_name = '' #now users can not enter a empty user_name
    while not user_name:
        user_name = input("Enter Name to Use for Account Access: ")
    for i in range(0, len(users)): #different loop to enable use of lower()
        while  user_name.lower() == users[i].lower(): #removes need for unique cases
            print("That User Already Exists!")
            user_name = '' #again stopping empty fields
            while not user_name:
                user_name = input("Enter Name to Use for Account Access: ")
    users.append(user_name)     
    print("Your Account Access Name is: " + user_name)

首先，我们可以创建一个循环来拒绝任何空白user_name。

接下来我们可以在检查user_name 是否存在于users[] 时使用.lower()。通过这样做，我们可以保留用户想要用来存储其姓名的唯一大小写格式（可能用于显示目的），但同时我们可以检查user_name 是否已经存在，无论大小写格式如何。

清理它，我们可以这样做：

 def ask_user(message=''): #create function to check for blank inputs
    user_name = ''
    while not user_name:
        user_name = input(message)
    return user_name

users = []
print("Welcome to The 'Create New User' Interface")
while True:
    user_name = ask_user("Enter Name to Use for Account Access: ")
    for i in range(0, len(users)):
        while  user_name.lower() == users[i].lower():
            print("\nThat User Already Exists!") #newline for clarity
            user_name = ask_user("Enter Name to Use for Account Access: ")
    users.append(user_name)     
    print("\nYour Account Access Name is: " + user_name) #newline for clarity

在这里我创建了处理空白输入的ask_user。然后在几个地方添加了\n 以帮助提高可读性。

输出

(xenial)vash@localhost:~/pcc/10$ python3 helping.py
Welcome to The 'Create New User' Interface
Enter Name to Use for Account Access: 
Enter Name to Use for Account Access: vash

Your Account Access Name is: vash
Enter Name to Use for Account Access: VASH

That User Already Exists!
Enter Name to Use for Account Access: 
Enter Name to Use for Account Access: p0seidon

Your Account Access Name is: p0seidon
Enter Name to Use for Account Access: P0SEidoN

That User Already Exists!

希望这会有所帮助！