Get Python Dictionary Values as List - Python

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.

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

[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.

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

[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.

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

[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.