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Python | Summation of dictionary list values
• Last Updated : 28 Aug, 2019

Sometimes, while working with Python dictionaries, we can have it’s values as lists. In this can we can have a problem that we just require the count of elements in those list as a whole. This can be a problem in Data Science in which we need to get total records in observations. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using `sum()` + list comprehension
This task can be performed using sum function which can be used to get the summation and internal list comprehension can provide a mechanism to iterate this logic to all the keys of dictionary.

 `# Python3 code to demonstrate working of``# Summation of dictionary list values``# using sum() + list comprehension`` ` `# initialize dictionary``test_dict ``=` `{``'gfg'` `: [``5``, ``6``, ``7``], ``'is'` `: [``10``, ``11``], ``'best'` `: [``19``, ``31``, ``22``]}`` ` `# printing original dictionary``print``(``"The original dictionary is : "` `+` `str``(test_dict))`` ` `# Summation of dictionary list values``# using sum() + list comprehension``res ``=` `sum``(``len``(sub) ``for` `sub ``in` `test_dict.values())`` ` `# printing result``print``(``"Summation of dictionary list values are : "` `+` `str``(res))`
Output :
```The original dictionary is : {'best': [19, 31, 22], 'is': [10, 11], 'gfg': [5, 6, 7]}
Summation of dictionary list values are : 8
```

Method #2 : Using `sum() + map()`
This task can also be performed using map function in place of list comprehension to extend the logic of finding the length, rest all the functionality remaining same as the above method.

 `# Python3 code to demonstrate working of``# Summation of dictionary list values``# using sum() + map()`` ` `# initialize dictionary``test_dict ``=` `{``'gfg'` `: [``5``, ``6``, ``7``], ``'is'` `: [``10``, ``11``], ``'best'` `: [``19``, ``31``, ``22``]}`` ` `# printing original dictionary``print``(``"The original dictionary is : "` `+` `str``(test_dict))`` ` `# Summation of dictionary list values``# using sum() + map()``res ``=` `sum``(``map``(``len``, test_dict.values()))`` ` `# printing result``print``(``"Summation of dictionary list values are : "` `+` `str``(res))`
Output :
```The original dictionary is : {'best': [19, 31, 22], 'is': [10, 11], 'gfg': [5, 6, 7]}
Summation of dictionary list values are : 8
```

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