# Python – Selective Key Values Summation

• Last Updated : 03 Jul, 2020

Sometimes, while working with Python dictionaries, we can have a problem in which we desire to get summation of certain keys’ values in dictionary. This kind of application can have usecase in many domains such as day-day programming. Let’s discuss certain ways in which this task can be performed.

Input : test_dict = {‘Gfg’ : 4, ‘is’ : 2, ‘best’ : 7}, key_list = [‘Gfg’, ‘best’]
Output : 11

Input : test_dict = {‘Gfg’ : 4, ‘best’ : 7}, key_list = [‘Gfg’]
Output : 4

Method #1 : Using loop
This is one of the ways in which this task can be performed. In this, we iterate for target list keys and sum the corresponding values from dictionary.

 `# Python3 code to demonstrate working of ``# Selective Key Values Summation``# Using loop`` ` `# initializing dictionary``test_dict ``=` `{``'Gfg'` `: ``4``, ``'is'` `: ``2``, ``'best'` `: ``7``, ``'for'` `: ``9``, ``'geeks'` `: ``10``} `` ` `# printing original dictionary``print``(``"The original dictionary is : "` `+` `str``(test_dict))`` ` `# initializing keys_list``key_list ``=` `[``'Gfg'``, ``'best'``, ``'geeks'``]`` ` `# Selective Key Values Summation``# Using loop``res ``=` `0`  `for` `key ``in` `key_list:``    ``res ``+``=` `test_dict[key]  ``         ` `# printing result ``print``(``"The keys summation : "` `+` `str``(res)) `

Output :

```The original dictionary is : {'Gfg': 4, 'is': 2, 'best': 7, 'for': 9, 'geeks': 10}
The keys summation : 21
```

Method #2 : Using `sum()` + list comprehension
The combination of above functions can be used to solve this problem. In this, we perform summation using sum() and list comprehension is used to perform task of iteration.

 `# Python3 code to demonstrate working of ``# Selective Key Values Summation``# Using sum() + list comprehension`` ` `# initializing dictionary``test_dict ``=` `{``'Gfg'` `: ``4``, ``'is'` `: ``2``, ``'best'` `: ``7``, ``'for'` `: ``9``, ``'geeks'` `: ``10``} `` ` `# printing original dictionary``print``(``"The original dictionary is : "` `+` `str``(test_dict))`` ` `# initializing keys_list``key_list ``=` `[``'Gfg'``, ``'best'``, ``'geeks'``]`` ` `# Selective Key Values Summation``# Using sum() + list comprehension``res ``=` `sum``([test_dict[key] ``for` `key ``in` `key_list])`` ` `# printing result ``print``(``"The keys summation : "` `+` `str``(res)) `

Output :

```The original dictionary is : {'Gfg': 4, 'is': 2, 'best': 7, 'for': 9, 'geeks': 10}
The keys summation : 21
```

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