# Python – Sort by Frequency of second element in Tuple List

• Last Updated : 02 Sep, 2020

Given list of tuples, sort by frequency of second element of tuple.

Input : test_list = [(6, 5), (1, 7), (2, 5), (8, 7), (9, 8), (3, 7)]
Output : [(1, 7), (8, 7), (3, 7), (6, 5), (2, 5), (9, 8)]
Explanation : 7 occurs 3 times as 2nd element, hence all tuples with 7, are aligned first.

Input : test_list = [(1, 7), (8, 7), (9, 8), (3, 7)]
Output : [(1, 7), (8, 7), (3, 7), (9, 8)]
Explanation : 7 occurs 3 times as 2nd element, hence all tuples with 7, are aligned first.

Method #1 : Using sorted() + loop + defaultdict() + lambda

In this, we compute the frequency using defaultdict() and use this result to pass as param to lambda function to perform sorting using sorted() on basis of it.

## Python3

 # Python3 code to demonstrate working of # Sort by Frequency of second element in Tuple List# Using sorted() + loop + defaultdict() + lambdafrom collections import defaultdict  # initializing listtest_list = [(6, 5), (2, 7), (2, 5), (8, 7), (9, 8), (3, 7)]  # printing original listprint("The original list is : " + str(test_list))  # constructing mappingfreq_map = defaultdict(int)for idx, val in test_list:    freq_map[val] += 1  # performing sort of result res = sorted(test_list, key = lambda ele: freq_map[ele[1]], reverse = True)  # printing resultsprint("Sorted List of tuples : " + str(res))

Output

The original list is : [(6, 5), (2, 7), (2, 5), (8, 7), (9, 8), (3, 7)]
Sorted List of tuples : [(2, 7), (8, 7), (3, 7), (6, 5), (2, 5), (9, 8)]

Method #2 : Using Counter() + lambda + sorted()

In this, the task of frequency computation is done using Counter(), rest all functionality is similar to above method.

## Python3

 # Python3 code to demonstrate working of # Sort by Frequency of second element in Tuple List# Using Counter() + lambda + sorted()from collections import Counter  # initializing listtest_list = [(6, 5), (2, 7), (2, 5), (8, 7), (9, 8), (3, 7)]  # printing original listprint("The original list is : " + str(test_list))  # constructing mapping using Counterfreq_map = Counter(val for key, val in test_list)  # performing sort of result res = sorted(test_list, key = lambda ele: freq_map[ele[1]], reverse = True)  # printing resultsprint("Sorted List of tuples : " + str(res))

Output

The original list is : [(6, 5), (2, 7), (2, 5), (8, 7), (9, 8), (3, 7)]
Sorted List of tuples : [(2, 7), (8, 7), (3, 7), (6, 5), (2, 5), (9, 8)]

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