Python – Replace all repeated occurrences with N

Sometimes, while working with Python list, we can have a problem in which we need to replace an element with another. But one can have variations of these such as increase of number and keeping the first occurrence. This can have applications in various domains. Lets discuss certain ways in which this task can be performed.

Method #1 : Using enumerate() + set() + loop
The combination of above functions can be used to perform this task. In this, we iterate the list and then store the 1st occurrence in set, the consecutive values are tested using in and replaced inplace.





# Python3 code to demonstrate 
# Replace all repeated occurrences of K with N
# using enumerate() + set() + loop
# Initializing list
test_list = [1, 3, 3, 1, 4, 4, 1, 5, 5]
# printing original list
print("The original list is : " + str(test_list))
# Initializing N 
N = 'rep'
# Replace all repeated occurrences of K with N
# using enumerate() + set() + loop
his = set([])
for idx, ele in enumerate(test_list):
    if ele in his:
        test_list[idx] = N
# printing result 
print ("The duplication altered list : " + str(test_list))


Output :

The original list is : [1, 3, 3, 1, 4, 4, 1, 5, 5]
The duplication altered list : [1, 3, 'rep', 'rep', 4, 'rep', 'rep', 5, 'rep']
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