Getting 'int' object is not iterable

Question

    cat_sums[cat] += value
TypeError: \'int\' object is not iterable

My input is this:

defaultdict(, {\'composed\'         


        

Answer 1

Each of your values is a list. The + operator, when applied to lists adds an iterable to a list. It doesn't append a single value:

>>> [1,2] + [3,4]
[1, 2, 3, 4]
>>> [1,2] + 3
TypeError: can only concatenate list (not "int") to list

It looks like you want to do cat_sums[cat].append(value).