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I'm trying to set the second appearance of a text in a list to 0. The first appearance of the word should remain untouched.

e.g.

Xlist=["dog", "cat", "horse", "dog"]

The outcome should look like this:

["dog", "cat", "horse", "0"]

Is there a simple way to do it? Since I'm new to python programming I can't really imagine how to do it and I didn't find a way in other threads.

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5
  • Find indices of dupes and set the values of those indices to 0 (except the first item which you want to keep in your case) Commented Feb 11, 2020 at 9:37
  • What about third appearance of an element? Should only 2nd appearance be set to 0? Commented Feb 11, 2020 at 9:43
  • This problem is not very well defined. What should happen to this list: ["dog", "cat", "dog", "dog", "cat", "horse"]? Commented Feb 11, 2020 at 9:45
  • Looks like an exercise. Please provide what you have tried, why it isn't working, etc. Help-Center: how-to-ask Commented Feb 11, 2020 at 9:47
  • The answer @jaswanth has provided already solved my problem. Every appearance after the 2nd should be changed to "0". Sorry if that was misleading Commented Feb 12, 2020 at 8:31

1 Answer 1

Reset to default
1 
keys = set([])
for index, item in enumerate(data):
    if item in keys:
        data[index] = "0"
        continue
    keys.add(item)

print(data)

I hope this works for you

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2 Comments

I would recommend to use set data type for keys instead of a list.
Thanks, for people who did not understand It is better because the time complexity of searching in a set is less compared to a list that is why it is better to use set instead of list. edited the solution

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