def xxx(*args) where arguments may be any object. How to get sum of numbers in arguments?

Question

I have a function with arbitrary number of arguments and need to add those arguments when they are numbers or can be turned to numbers. Example:

def object_sum(*args):
    pass

print(object_sum(3, 'sun', '5', ['5', 'earth'], (5, '5')))
#Would print 23

Why isn't it `8`? You can't convert a list or tuple to a number. — Barmar, Oct 08 '21 at 20:30
@Barmar lol, are you a teacher ? Your question is pedagogically perfect for StackOverflow beginners ! — TheEagle, Oct 08 '21 at 20:31
Is `['5', 'earth']` not a number or do you want to iterate that sequence and get its numbers? How many levels of nesting? Is there a list in a list in a list? — tdelaney, Oct 08 '21 at 20:32
Loop over the arguments. Try to convert it to a number. Use `try/except` to catch if it fails. If it's iterable, call the function recursively with that as the arguments. — Barmar, Oct 08 '21 at 20:33
@Programmer - Its an important question. Should sequences be iterated? Which sequences? It can end up infinite. A sequence that iterates iterable sequences forever.. `str` is that way. — tdelaney, Oct 08 '21 at 20:35

Dani Mesejo · Answer 1 · 2021-10-08T20:40:48.463

1

Assuming you want to catch the nested integers, do:

from collections.abc import Iterable


def object_sum(*args):
    def flatten(l):
        # https://stackoverflow.com/a/2158532/4001592
        for el in l:
            if isinstance(el, Iterable) and not isinstance(el, (str, bytes)):
                yield from flatten(el)
            else:
                try:
                    yield int(el)
                except ValueError:
                    yield 0

    return sum(flatten(args))


print(object_sum(3, 'sun', '5', ['5', 'earth'], (5, '5')))

Output

edited Oct 08 '21 at 20:40

answered Oct 08 '21 at 20:33

Dani Mesejo

61,499
6
49
76

2

I don't think this works correctly for multi-character strings, because `iter(i)` will iterate over the digits. – Barmar Oct 08 '21 at 20:35
you need to try `int(i)` first, then use `iter(i)` in the `except` – Barmar Oct 08 '21 at 20:36
@Barmar Updated the answer – Dani Mesejo Oct 08 '21 at 20:41

score 0 · Answer 2 · answered Oct 08 '21 at 20:47

Test if the argument is a list or similar, if yes, recurse into it, if not, try to convert it to an integer:

def object_sum(*args):
    result = 0
    for arg in args:
        arg_type = type(arg)
        if arg_type in (list, tuple, set, range):
            result += object_sum(*arg) # The asterisk is important - without it, the recursively called function would again call itself, and we'd get a RecursionError
        else:
            try:
                result += int(arg) # Try to convert to int
            except ValueError:
                pass # arg is not convertable, skip it
    return result

print(object_sum(3, 'sun', '5', ['5', 'earth'], (5, '5')))

Output:

def xxx(*args) where arguments may be any object. How to get sum of numbers in arguments?

2 Answers2