Convert List of Lists to Dictionary - Python

Get Python Dictionary Values as List – Python

Last Updated : 07 Feb, 2025

We are given a dictionary where the values are lists and our task is to retrieve all the values as a single flattened list. For example, given the dictionary: d = {“a”: [1, 2], “b”: [3, 4], “c”: [5]} the expected output is: [1, 2, 3, 4, 5]

Using itertools.chain()

itertools.chain() function efficiently combines multiple lists into a single iterable without extra memory overhead.

Python

from itertools import chain

d = {"a": [1, 2], "b": [3, 4], "c": [5]}
res = list(chain(*d.values()))

print(res)

Output

[1, 2, 3, 4, 5]

Explanation:

d.values() retrieves all the dictionary values as separate lists and chain(*d.values()) flattens them efficiently.
list() converts the result into a list.

Using sum()

sum() function can concatenate all lists into a single flattened list.

Python

d = {"a": [1, 2], "b": [3, 4], "c": [5]}
res = sum(d.values(), [])

print(res)

Output

[1, 2, 3, 4, 5]

Explanation:

d.values() retrieves all dictionary values as separate lists.
sum(d.values(), []) flattens them by adding each list to an empty list ([]).

Using List Comprehension

List comprehension allows us to flatten dictionary values into a single list in a readable way.

Python

d = {"a": [1, 2], "b": [3, 4], "c": [5]}
res = [val for sublist in d.values() for val in sublist]

print(res)

Output

[1, 2, 3, 4, 5]

Explanation:

d.values() retrieves all dictionary values as separate lists and the first loop iterates over each list (sublist).
whereas the second loop extracts each element (val) from the sublist and adds it to res.

Convert List of Lists to Dictionary - Python

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