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Python – Remove alternate consecutive duplicates
  • Last Updated : 01 Aug, 2020

Given list of elements, remove alternate consecutive duplicates of elements.

Input : test_list = [5, 5, 5, 5, 6, 6]
Output : [5, 5, 6]
Explanation : Alternate occ. of 5 and 6 are removed.

Input : test_list = [5, 5, 5, 5]
Output : [5, 5]
Explanation : Alternate occ. of 5 are removed.

Method : Using loop + remove()

The combination of above functions can be used to solve this problem. In this, we iterate each element and use additional previous element variable to keep track of alternate criteria. The removal is performed using remove().



Python3

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# Python3 code to demonstrate working of 
# Remove alternate consecutive duplicates
# Using loop + remove()
  
# initializing lists
test_list = [5, 5, 5, 5, 6, 6, 8, 3, 3, 8]
  
# printing original list
print("The original list : " + str(test_list))
  
# Using loop to iterate through elements
# element to keep track
temp = test_list[0]
count = 0
org_list = test_list
idx = 0
while(1):
      
    # break when idx greater than size
    if idx >= len(org_list):
        break
      
    # check for alternates 
    if count % 2 and temp == test_list[idx]:
        test_list.remove(test_list[idx])
        idx = idx - 1
        count += 1
        temp = test_list[idx]
    else:
          
        # keeping track of alternate index increment
        # and assignment
        if temp != test_list[idx]:
            count = 1
            temp = test_list[idx]
        else :
            count += 1
    idx = idx + 1
  
# printing result 
print("List after alternate duplicates removal : " + str(test_list))

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Output

The original list : [5, 5, 5, 5, 6, 6, 8, 3, 3, 8]
List after alternate duplicates removal : [5, 5, 6, 8, 3, 8]

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