How to make a nested dictionary and dynamically append data

Question

I have a loop giving me three variables

matteGroup
matteName
object

I would like to make a nested dicionary holding all the data like:

Answer 1

Look at the defaultdict in the collections module.

Here's a simple example that looks like what you're going for:

>>> from collections import defaultdict
>>> dizGroup = defaultdict(lambda:defaultdict(list))
>>> dizGroup['group1']['name1'].append(1)
>>> dizGroup['group1']['name1'].append(2)
>>> dizGroup['group1']['name1'].append(3)
>>> dizGroup['group1']['name2'].append(4)
>>> dizGroup['group1']['name2'].append(5)
>>> dizGroup['group2']['name1'].append(6)
>>> dizGroup
defaultdict( at 0x7ffcb5ace9b0>, {'group1': defaultdict(, {'name2': [4, 5], 'name1': [1, 2, 3]}), 'group2': defaultdict(, {'name1': [6]})})

So, you should just need this:

if mc.objExists(obj + ('.matteGroup')):
   matteGroup = mc.getAttr(obj + ('.matteGroup'))
   matteName = mc.getAttr(obj + ('.matteName'))
   dizGroup[matteGroup][matteName].append(obj)