“object of type 'NoneType' has no len()” error

Question

I\'m seeing weird behavior on this code:

images = dict(cover=[],second_row=[],additional_rows=[])

for pic in pictures:
    if len(images[\'cover\']) == 0:
              


        

Answer 1

The first time you assign: images['cover'] = pic.path_thumb_l, it replaces the value of the empty list initially stored in images['cover'] with the value of pic.path_thumb_l which is None.

Maybe your code in this line must be images['cover'].append(pic.path_thumb_l)

Answer 2

You assign something new to images['cover']:

images['cover'] = pic.path_thumb_l

where pic.path_thumb_l is None at some point in your code.

You probably meant to append instead:

images['cover'].append(pic.path_thumb_l)

Answer 3

your problem is that

if len(images['cover']) == 0:

checks the LENGTH of the value of images['cover'] what you meant to do is check if it HAS a value.

do this instead:

if not images['cover']: