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

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() + lambda ` `from` `collections ``import` `defaultdict ` ` `  `# initializing list ` `test_list ``=` `[(``6``, ``5``), (``2``, ``7``), (``2``, ``5``), (``8``, ``7``), (``9``, ``8``), (``3``, ``7``)] ` ` `  `# printing original list ` `print``(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# constructing mapping ` `freq_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 results ` `print``(``"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 list ` `test_list ``=` `[(``6``, ``5``), (``2``, ``7``), (``2``, ``5``), (``8``, ``7``), (``9``, ``8``), (``3``, ``7``)] ` ` `  `# printing original list ` `print``(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# constructing mapping using Counter ` `freq_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 results ` `print``(``"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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