Python | Count unique sublists within list

Last Updated : 25 Apr, 2023

Given a list of lists, the task is to find the count of unique sublists within list. Examples:

Input: [['Geek', 'for', 'geeks'], ['geeks', 'for'],
        ['for', 'Geeks', 'geek'], ['Geek', 'for', 'geeks']]

Output:
{('geeks', 'for'): 1, ('for', 'Geeks', 'geek'): 1, 
 ('Geek', 'for', 'geeks'): 2}

Below are some ways to achieve the task. Method #1: Using Iteration

Python3

# Python code to count unique sublist within list

# Input list initialization
Input = [['Geek', 'for', 'geeks'], ['geeks', 'for'],
         ['for', 'Geeks', 'geek'], ['Geek', 'for', 'geeks']]

# Output list initialization
Output = {}

# Using Iteration
for lis in Input:
    Output.setdefault(tuple(lis), list()).append(1)
for a, b in Output.items():
    Output[a] = sum(b)

# Printing output
print(Output)

Output:

{('Geek', 'for', 'geeks'): 2, ('geeks', 'for'): 1, ('for', 'Geeks', 'geek'): 1}

Time Complexity: O(n)
Auxiliary Space: O(n)

Method #2: Using Counter

Python3

# Python code to find count of unique list in list of list

# Importing counter from collection
from collections import Counter

# Input list initialization
lst = [[1, 2, 3], [4, 5, 6], [3, 2, 1], [1, 2, 3]]

# Using counter
Output = Counter([tuple(i) for i in lst])

# Printing output
print(Output)

Output:

Counter({(1, 2, 3): 2, (3, 2, 1): 1, (4, 5, 6): 1})

Time Complexity: O(n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(1), constant space needed

Method #3: Using Pandas

Python3

# Python code to count unique sublist within list

# Importing 
from collections import Counter
import pandas as pd                     

# Input list initialization
lst = [[1, 2, 3], [4, 5, 6], [3, 2, 1], [1, 2, 3]]

# Getting count
dict = Counter([tuple(i) for i in lst])

# Creating pandas dataframe
Output = pd.DataFrame(data ={'list': list(dict.keys()),
                         'count': list(dict.values())})

# Printing output
print(Output)

Output:

count       list
0      1  (3, 2, 1)
1      1  (4, 5, 6)
2      2  (1, 2, 3)

Time Complexity: O(n), where n is the length of the list
Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the list