summing only the numbers contained in a list

Question

Give a method that sums all the numbers in a list. The method should be able to skip elements that are not numbers. So, sum([1, 2, 3]) should be

Answer 1

def filtersum(L):
    if not L: return 0
    if not isinstance(L[0], int): return filtersum(L[1:])
    return L[0] + filtersum(L[1:])

Output:

In [28]: filtersum([1,2,3])
Out[28]: 6

In [29]: filtersum([1,'A', 2,3])
Out[29]: 6