Python | Remove duplicates from nested list

The task of removing duplicates many times in recent past, but sometimes when we deal with the complex data structure, in those cases we need different techniques to handle this type of problem. Let’s discuss certain ways in which this task can be achieved.

Method #1 : Using sorted() + set()
This particular problem can be solved using the above functions. The idea here is to sort the sublist and then removing the like elements using the set operations which removes duplicates.

# Python3 code to demonstrate
# removing duplicate sublist
# using set() + sorted()

# initializing list
test_list = [[1, 0, -1], [-1, 0, 1], [-1, 0, 1],
                           [1, 2, 3], [3, 4, 1]]

# printing original list
print("The original list : " + str(test_list))

# using set() + sorted()
# removing duplicate sublist
res = list(set(tuple(sorted(sub)) for sub in test_list))

# print result
print("The list after duplicate removal : " + str(res))

Output :

The original list : [[1, 0, -1], [-1, 0, 1], [-1, 0, 1], [1, 2, 3], [3, 4, 1]]
The list after duplicate removal : [(-1, 0, 1), (1, 3, 4), (1, 2, 3)]

Method #2 : Using set() + map() + sorted()
The task performed by the list comprehension in the above method can be modified using the map function using lambda functions to extend the logic to each and every sublist.

# Python3 code to demonstrate
# removing duplicate sublist
# using set() + map() + sorted()

# initializing list
test_list = [[1, 0, -1], [-1, 0, 1], [-1, 0, 1],
                           [1, 2, 3], [3, 4, 1]]

# printing original list
print("The original list : " + str(test_list))

# using set() + map() + sorted()
# removing duplicate sublist
res = list(set(map(lambda i: tuple(sorted(i)), test_list)))

# print result
print("The list after duplicate removal : " + str(res))

Output :

The original list : [[1, 0, -1], [-1, 0, 1], [-1, 0, 1], [1, 2, 3], [3, 4, 1]]
The list after duplicate removal : [(-1, 0, 1), (1, 3, 4), (1, 2, 3)]