How to apply a function to each sublist of a list in python?

Question

Lets say I have a list like this:

list_of_lists = [[\'how to apply\'],[\'a function\'],[\'to each list?\']]

And I have a function let\'s sa

Answer 1

Map is your friend! map takes a function and an iterable (list, for example) and applies the function on each element of the list.

map(len, [['how to apply'],['a function'],['to each list?']]) 

Output

[1, 1, 1]

If you wanted to do more granular calculation on elements of the sublist, you can nest the map:

map(lambda x: map(lambda y: y + 1, x), [[1], [1, 2], [1, 2, 3]])

Output

[[2], [2, 3], [2, 3, 4]]

Another possible approach (also from functional programming) are list comprehensions. List comprehension is a way of constructing a list from iterable in Python. The syntax is [element for element in iterable]. Any computation can be done on the element, so

[f(element) for element in iterable]

means that the resulting list will be a list of elements, where each element is the result of function f. Like map, list comprehension can be further nested, resulting in a nested element function application.

[element + 1 for element in el] for el in [[1], [1, 2], [1, 2, 3]]]

Output

[[2], [2, 3], [2, 3, 4]]