CODEWITHSUNDEEP
python-3.xlist
Dasa
Dasa

Reputation: 1

Check if an certain element appears twice in a list - Python

Without importing another function check if a list contains two of the same element

F.E list = [3,4,5,3] since 3 appears twice in the list return True

Thanks for the help

Upvotes: 0

Views: 13048

Answers (3)

user11697799
user11697799

Reputation:

There are different approaches to solve this problem.

Solution 1: Use set()

if len(set(<your_list>))<len(<your_list>):
    return False
else:
    return True

Solution 2 : Use hash dictionary

def check_list(lst):
   hash_dict={}
   for elem in lst:
     if elem not in hash_dict:
        hash_dict[elem]=1
     else:
        return True
    return False

In the above solution, we add the elements in the hash dict and constantly check if it exists there, if it does then we return True. If the list has no duplicate or more than 2 elements then it will just return false.

Solution 3 : We can also use counter from collections

from collections import Counter
new_dict=Counter(<your list>)
return True if 2 in new_dict.values() else False

Upvotes: 0

ssharma
ssharma

Reputation: 150

If you need to check if the element occurs exactly twice, you could do this:

l = [3,4,5,3]
if 2 in set([l.count(n) for n in l]):
    print('True')

Upvotes: 2

a_guest
a_guest

Reputation: 36329

You can convert to set and check the resulting length:

len(set(data)) < len(data)

Upvotes: 3

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