Python | Remove duplicate tuples from list of tuples
Last Updated :
16 Mar, 2023
Given a list of tuples, Write a Python program to remove all the duplicated tuples from the given list.
Examples:
Input : [(1, 2), (5, 7), (3, 6), (1, 2)]
Output : [(1, 2), (5, 7), (3, 6)]
Input : [('a', 'z'), ('a', 'x'), ('z', 'x'), ('a', 'x'), ('z', 'x')]
Output : [('a', 'z'), ('a', 'x'), ('z', 'x')]
Method #1 : List comprehension This is a naive approach to use list comprehension. Here, we use two for loops and set data structure to cancel out all the duplicates.
Python3
def removeDuplicates(lst):
return [t for t in (set(tuple(i) for i in lst))]
lst = [(1, 2), (5, 7), (3, 6), (1, 2)]
print(removeDuplicates(lst))
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Output:
[(1, 2), (5, 7), (3, 6)]
Time complexity: O(n*logn), where n is the length of the input list.
Auxiliary space: O(n), where n is the length of the input list.
Method #2 : List comprehension (Efficient approach) This method is efficient as compared to the above method, here we use a single for loop within list comprehension and then convert it to set to remove duplicates and then again convert it to list.
Python3
def removeDuplicates(lst):
return list(set([i for i in lst]))
lst = [(1, 2), (5, 7), (3, 6), (1, 2)]
print(removeDuplicates(lst))
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Output:
[(1, 2), (5, 7), (3, 6)]
Time complexity: O(n) where n is the number of tuples in the list.
Auxiliary space: O(n).
Method #3 : Python enumerate() method
Python3
def removeDuplicates(lst):
return [[a, b] for i, [a, b] in enumerate(lst)
if not any(c == b for _, c in lst[:i])]
lst = [(1, 2), (5, 7), (3, 6), (1, 2)]
print(removeDuplicates(lst))
|
Output:
[[1, 2], [5, 7], [3, 6]]
Time complexity: O(n^2), where n is the length of the input list.
Auxiliary space: O(n^2).
Method #4: Using a dictionary
This method involves creating a dictionary where the keys are the tuples, and the values are a boolean indicating whether the tuple has been encountered before. We can then iterate through the list and add the tuples to the result list if they have not been encountered before.
Python3
def remove_duplicates(lst):
encountered = {}
result = []
for tup in lst:
if tup not in encountered:
encountered[tup] = True
result.append(tup)
return result
lst = [(1, 2), (5, 7), (3, 6), (1, 2)]
print(remove_duplicates(lst))
|
Output
[(1, 2), (5, 7), (3, 6)]
Time complexity: O(n), where n is the number of tuples in the list.
Auxiliary Space: O(n), as we are creating a dictionary with n keys.
Method #5: Using recursive function.
Python3
def remove_duplicate(start,oldlist,newlist):
if start==len(oldlist):return newlist
if oldlist[start] not in newlist:
newlist.append(oldlist[start])
return remove_duplicate(start+1,oldlist,newlist)
lst = [(1, 2), (5, 7), (3, 6), (1, 2)]
res=remove_duplicate(0,lst,[])
print(res)
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Output
[(1, 2), (5, 7), (3, 6)]
Time complexity: O(n), where n is the number of tuples in the list.
Auxiliary Space: O(n), as we are creating a n function call.
Method #6:Using the dict.fromkeys
Python3
def removeDuplicates(lst):
dict_without_duplicates = dict.fromkeys(lst)
return list(dict_without_duplicates.keys())
lst = [(1, 2), (5, 7), (3, 6), (1, 2)]
print(removeDuplicates(lst))
|
Output
[(1, 2), (5, 7), (3, 6)]
Time complexity: O(n)
Auxiliary Space: O(n)
Method #7: Using the itertools library
The itertools library provides a function called “groupby” that can be used to group similar items together. We can use this function to group the tuples by their elements, which effectively removes duplicates.
Python3
import itertools
def removeDuplicates(lst):
lst.sort()
grouped = itertools.groupby(lst)
unique = [key for key,_ in grouped]
return unique
lst = [(1, 2), (5, 7), (3, 6), (1, 2)]
print(removeDuplicates(lst))
|
Output
[(1, 2), (3, 6), (5, 7)]
Time complexity: O(n log n), where n is the length of the input list.
Auxiliary space: O(n), where n is the length of the input list.
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