检查用户输入后的 While/For/If Else 循环

Question

I'm new to Python and learning. I try to write a code

1. User input full name (with space)
2. Check duplication to a list (I used split and join to compare strings)
3. If find a duplication, re-input new name
4. If not, simple break the loop and print "Thanks"
5. I only need to print "Duplicated" or "Thanks" 1 time, not multiple times with For loop:(.

My issue when I cant re-call the input with my code (with duplicated input) or break the loop (after new name)

list=["MT", "Smith Jenkins", "PT", "CP"]

while True:
    user=input("Your full name :")
    usercheck="".join(user.split())
    print(usercheck)

    for i in list:
        j="".join(i.split())
        if usercheck ==j:
            print("Duplicated ! Please enter new name")   
            
        else:
            print("Thanks")
        break 

Thank you.

Answer 1

You need to think about that

• if the current name in the iteratation is same:that's a dup
• if the current name is different: you can't conclude there is not dup now, you need to test the others

---

So you can use the for/else construction, the else will be executed if no break has been seen in the loop, in your case if no duplicated has been found, there you'll be able to break the while loop

names = []
while True:
    user = input("Your full name :")
    usercheck = "".join(user.split())
    print(usercheck)
    for name in names:
        j = "".join(name.split())
        if usercheck == j:
            print("Duplicated ! Please enter new name")
            break
    else:
        print("Thanks")
        break

---

If that is too tricky, you can keep with a variable that will help you know whether you've seen a duplicate or not

while True:
    user = input("Your full name :")
    usercheck = "".join(user.split())
    duplicated = False
    for name in names:
        j = "".join(name.split())
        if usercheck == j:
            print("Duplicated ! Please enter new name")
            duplicated = True
            break
    if duplicated:
        print("Thanks")
        break