# Python | Aggregate values by tuple keys

• Last Updated : 29 Oct, 2019

Sometimes, while working with records, we can have a problem in which we need to group the like keys and aggregate the values of like keys. This can have application in any kind of scoring. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using `Counter()` + generator expression
The combination of above functions can be used to perform this particular task. In this, we need to first combine the like key elements and task of aggregation is performed by `Counter()`.

 `# Python3 code to demonstrate working of``# Aggregate values by tuple keys``# using Counter() + generator expression``from` `collections ``import` `Counter`` ` `# initialize list``test_list ``=` `[(``'gfg'``, ``50``), (``'is'``, ``30``), (``'best'``, ``100``), ``                          ``(``'gfg'``, ``20``), (``'best'``, ``50``)]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Aggregate values by tuple keys``# using Counter() + generator expression``res ``=` `list``(Counter(key ``for` `key, num ``in` `test_list ``                  ``for` `idx ``in` `range``(num)).items())`` ` `# printing result``print``(``"List after grouping : "` `+` `str``(res))`

Output :

```The original list is : [('gfg', 50), ('is', 30), ('best', 100), ('gfg', 20), ('best', 50)]
List after grouping : [('best', 150), ('gfg', 70), ('is', 30)]
```

Method #2 : Using `groupby() + map() + itemgetter() + sum()`
The combination of above functions can also be used to perform this particular task. In this, we group the elements using groupby(), decision of key’s index is given by itemgetter. Task of addition(aggregation) is performed by sum() and extension of logic to all tuples is handled by map().

 `# Python3 code to demonstrate working of``# Aggregate values by tuple keys``# using groupby() + map() + itemgetter() + sum()``from` `itertools ``import` `groupby``from` `operator ``import` `itemgetter`` ` `# initialize list``test_list ``=` `[(``'gfg'``, ``50``), (``'is'``, ``30``), (``'best'``, ``100``),``                          ``(``'gfg'``, ``20``), (``'best'``, ``50``)]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Aggregate values by tuple keys``# using groupby() + map() + itemgetter() + sum()``res ``=` `[(key, ``sum``(``map``(itemgetter(``1``), ele)))``       ``for` `key, ele ``in` `groupby(``sorted``(test_list, key ``=` `itemgetter(``0``)), ``                                                ``key ``=` `itemgetter(``0``))]`` ` `# printing result``print``(``"List after grouping : "` `+` `str``(res))`

Output :

```The original list is : [('gfg', 50), ('is', 30), ('best', 100), ('gfg', 20), ('best', 50)]
List after grouping : [('best', 150), ('gfg', 70), ('is', 30)]
```

My Personal Notes arrow_drop_up