# Python | Value summation of key in dictionary

• Last Updated : 26 Aug, 2019

Many operations such as grouping and conversions are possible using Python dictionaries. But sometimes, we can also have a problem in which we need to perform the aggregation of values of key in dictionary list. This task is common in day-day programming. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using` sum()` + list comprehension

This is the one-liner approach to perform the task of getting the sum of particular key while iterating to the similar keys in list of dictionaries using list comprehension.

 `# Python3 code to demonstrate working of``# Value summation of key in dictionary``# Using sum() + list comprehension`` ` `# Initialize list``test_list ``=` `[{``'gfg'` `: ``1``, ``'is'` `: ``2``, ``'best'` `: ``3``},``             ``{``'gfg'` `: ``7``, ``'is'` `: ``3``, ``'best'` `: ``5``},``             ``{``'gfg'` `: ``9``, ``'is'` `: ``8``, ``'best'` `: ``6``}] `` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Value summation of key in dictionary``# Using sum() + list comprehension``res ``=` `sum``(sub[``'gfg'``] ``for` `sub ``in` `test_list)`` ` `# printing result``print``(``"The sum of particular key is : "` `+` `str``(res))`

Output :

The original list is : [{‘best’: 3, ‘gfg’: 1, ‘is’: 2}, {‘best’: 5, ‘gfg’: 7, ‘is’: 3}, {‘best’: 6, ‘gfg’: 9, ‘is’: 8}]
The sum of particular key is : 17

Method #2 : Using `sum() + itemgetter() + map()`
The combination of these functions can also be used to perform this task. In this, the main difference is that the comprehension task is done by `map()` and the key access task is done by the `itemgetter().`

 `# Python3 code to demonstrate working of``# Value summation of key in dictionary``# Using sum() + itemgetter() + map()``import` `operator`` ` `# Initialize list``test_list ``=` `[{``'gfg'` `: ``1``, ``'is'` `: ``2``, ``'best'` `: ``3``},``             ``{``'gfg'` `: ``7``, ``'is'` `: ``3``, ``'best'` `: ``5``},``             ``{``'gfg'` `: ``9``, ``'is'` `: ``8``, ``'best'` `: ``6``}] `` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# Value summation of key in dictionary``# Using sum() + itemgetter() + map()``res ``=` `sum``(``map``(operator.itemgetter(``'gfg'``), test_list))`` ` `# printing result``print``(``"The sum of particular key is : "` `+` `str``(res))`

Output :

The original list is : [{‘best’: 3, ‘gfg’: 1, ‘is’: 2}, {‘best’: 5, ‘gfg’: 7, ‘is’: 3}, {‘best’: 6, ‘gfg’: 9, ‘is’: 8}]
The sum of particular key is : 17

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