sum of nested list in Python

Question

I try to sum a list of nested elements

e.g, numbers=[1,3,5,6,[7,8]] should produce sum=30

I wrote the following code :

Answer 1

A quick recursion that uses a lambda to handle the nested lists:

rec = lambda x: sum(map(rec, x)) if isinstance(x, list) else x

rec, applied on a list, will return the sum (recursively), on a value, return the value.

result = rec(a)