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Python – Group Tuples by Kth Index Element
• Last Updated : 03 Jul, 2020

Sometimes, while working with Python records, we can have a problem in which we need to perform grouping of elements of tuple by similar Kth index element. This kind of problem can have application in web development domain. Let’s discuss certain way in which this task can be performed.

Input : test_list = [(4, 5), (3, 2), (2, 2), (1, 2), (5, 5)], K = 0
Output : [((1, 2), ), ((2, 2), ), ((3, 2), ), ((4, 5), ), ((5, 5), )]

Input : test_list = [(4, 5), (3, 2), (2, 2)], K = 1
Output : [((2, 2), (3, 2)), ((4, 5), )]

Method : Using `groupby() + itemegetter()` + generator expression
The combination of above functions can be used to solve this problem. In this, we perform the task of grouping the elements from Kth index extracted using itemgetter and generator expression is used to bind whole logic together.

 `# Python3 code to demonstrate working of ``# Group Tuples by Kth Index Element``# Using groupby() + itemegetter() + generator expression``from` `operator ``import` `itemgetter``from` `itertools ``import` `groupby`` ` `# initializing lists``test_list ``=` `[(``4``, ``5``), (``3``, ``2``), (``2``, ``2``), (``1``, ``2``), (``5``, ``5``)]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing K ``K ``=` `1`` ` `# Group Tuples by Kth Index Element``# Using groupby() + itemegetter() + generator expression``test_list.sort()``res ``=` `list``(``tuple``(sub) ``for` `idx, sub ``in` `groupby(test_list, key ``=` `itemgetter(K)))`` ` `# printing result ``print``(``"Tuples after grouping : "` `+` `str``(res))`
Output :

```The original list is : [(4, 5), (3, 2), (2, 2), (1, 2), (5, 5)]
Tuples after grouping : [((1, 2), (2, 2), (3, 2)), ((4, 5), (5, 5))]
```

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