Sum of Integers - 'int' object is not iterable

Question

My question is related to the sum function in python.

So my code is

def black_jack(a, b):
    if sum(a, b) > 21:
        return 0
    else:
        return sum(a, b)


print black_jack(10, 5)

I get an error reading:

'int' object is not iterable

Can someone explain why this happens and how to fix it?

Answer 1

sum is builtin function, look at the documentation:

In [1]: sum?
Docstring:
sum(sequence[, start]) -> value

Return the sum of a sequence of numbers (NOT strings) plus the value
of parameter 'start' (which defaults to 0).  When the sequence is
empty, return start.
Type:      builtin_function_or_method

so you need to pass it a iterable! :
solution1

sum([a, b]) #list

solution2

sum((a, b)) #tuple

Answer 2

What's wrong with just the following?

def black_jack(a, b):
    if a + b > 21:
        return 0
    else:
        return a + b

print black_jack(10, 5)

In Blackjack, one can have much more than just two cards, but with your example, it appears that you assume that a hand can have only two cards. If you allow for a variable number of cards, then you'd need to use an iterable object as others have suggested:

def black_jack(values):
    total = sum(values)
    return 0 if total > 21 else total

print black_jack(10, 5)

From the documentation for sum():

sum(iterable[,start])

Sums start and the items of an iterable from left to right and returns the total. start defaults to 0. The iterable's items are normally numbers, and the start value is not allowed to be a string.

For some use cases, there are good alternatives to sum(). The preferred, fast way to concatenate a sequence of strings is by calling ''.join(sequence). To add floating point values with extended precision, see math.fsum(). To concatenate a series of iterables, consider using itertools.chain().

New in version 2.3.

Answer 3

Look at the documentation:

sum(iterable[, start])

Sums start and the items of an iterable from left to right and returns the total. start defaults to 0. The iterable‘s items are normally numbers, and the start value is not allowed to be a string.

So you have to pass an iterable as argument, not an int!

sum((a, b)) should work correctly.

This is a function which is intended to be used when you have many values stored in a list (for example), if you want to sum two values, you should simply use a + b.