apply a function over each element of an iterable with sublists

Question

I'm trying to apply a function to every element of a list containing arbitrary sub-levels of sublists. Like so.

a = [1,2,3]
b = [[1,2,3],[4,5,6]]
c = [[[1,2,3],[4,5,6]],[[7,8,9],[10,11,12]]]

function = lambda x: x+1
def apply(iterable,f): 
    # do stuff here

print(apply(a,function)) # [2,3,4]
print(apply(b,function)) # [[2,3,4],[5,6,7]]
print(apply(c,function)) # [[[2,3,4],[5,6,7]],[[8,9,10],[11,12,13]]]

basically i can't find a way to write the apply function. I tried with numpy, but that's not the solution, of course, because the contents of the list could also be strings, objects ...

Answer 1

Sounds like recursion should be able to solve that:

a = [1,2,3]
b = [[1,2,3], [4,5,6]]
c = [[[1,2,3], [4,5,6]], [[7,8,9], [10,11,12]]]


f = lambda x : x+1

def apply(iterable, f): 
    # suggestion by Jérôme:
    # from collections.abc import Iterable and use
    # isinstance(iterable, collections.abc.Iterable) so it works for tuples etc. 
    if isinstance(iterable, list):
        # apply function to each element
        return [apply(w, f) for w in iterable]
    else:
        return f(iterable)

print(apply(a, f)) # [2,3,4]
print(apply(b, f)) # [[2,3,4],[5,6,7]]
print(apply(c, f)) # [[[2,3,4],[5,6,7]],[[8,9,10],[11,12,13]]]