Is there a way to prevent duplicates of an item in a list?

Question

I'm working on a project that requires the user to input names of players into a list. Is there any way to prevent the same name from being inputted?

Code I have so far:

#Team 1 naming
        print("Team 1 player input")
        elem = int(input("Amount of players: "))
        for i in range(0, elem):
            Team1_list.append(str(input(f'Enter player number {num_team1} name (In batting order) eg J.Smith: ')))
            num_team1 = num_team1 + 1
        print(Team1_list)

I've tried some things but none seem to work

Does this answer your question? [Removing duplicates in the lists](https://stackoverflow.com/questions/7961363/removing-duplicates-in-the-lists) — sushanth, Oct 25 '20 at 04:15

score 0 · Accepted Answer · answered Oct 25 '20 at 03:56

If you want the user to retry the entry, you can use something like this:

print("Team 1 player input")
elem = int(input("Amount of players: "))
for i in range(0, elem):
    p = None
    while not p or p in Team1_list:
        p = input(f'Enter player number {num_team1} name (In batting order) eg J.Smith: ')
        if p in Team1_list: print('That player already entered, please retry...')
    Team1_list.append(p)
    num_team1 = num_team1 + 1
print(Team1_list)

score 0 · Answer 2 · answered Oct 25 '20 at 04:03

If you're using Python 3.6+, you will have the benefit of dict keys are remembering your insert order. So you get benefit of both the list and set at the same. Consider the following:

#Team 1 naming
print("Team 1 player input")
elem = int(input("Amount of players: "))
team = {}
while len(team) < elem:
    num_team1 = len(team)+1
    name = str(input(f'Enter player number {num_team1} name (In batting order) eg J.Smith: ')))
    team[name] = 1
print(list(team.keys()))

If you enter the same name again, your num_team1 will not increment and your "list" will ignore that duplicated entry (i.e. keep only the first in its original order)

score 0 · Answer 3 · edited Oct 25 '20 at 04:16

0

Use a set with set{}

no_duplicates = {1, 2, 1, 3, 2}
print(no_duplicates)

{1, 2, 3}

edited Oct 25 '20 at 04:16

sushanth

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answered Oct 25 '20 at 04:03

Said Bristina

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You should make clear that using a set means losing the order of the items. – Klaus D. Oct 25 '20 at 05:29

Is there a way to prevent duplicates of an item in a list?

3 Answers3