MeldDict 
A dict subclass that supports adding and subtracting other Mappings to perform recursive merging and removal.
By default, lists are also melded, but this can be configured. You can also have keys whose values are empty after a subtraction dropped automatically.
The full documentation is available online at: https://melddict.readthedocs.io/
Examples
You can add two mappings together to combine them:
meld_dict = MeldDict({'a': 'a',
'b': [1, 2],
'c': {'1': 1},
'd': 'd'})
norm_dict = {'b': [3, 4],
'c': {'2': 2},
'd': 'D',
'e': 'e'}
meld_res = meld_dict + norm_dict
meld_res == {'a': 'a',
'b': [1, 2, 3, 4],
'c': {'1': 1, '2': 2},
'd': 'D',
'e': 'e'}
meld_dict += norm_dict # a.k.a. meld_dict.add(norm_dict)
meld_dict == meld_resYou can also subtract one mapping from another:
meld_dict = MeldDict({'a': 'a',
'b': [1, 2],
'c': {'1': 1, '2': 2},
'd': 'd'})
norm_dict = {'b': [2, 3],
'c': {'2': 2, '3': 3},
'd': 'D',
'e': 'e'}
meld_res = meld_dict - norm_dict
meld_res == {'a': 'a',
'b': [1],
'c': {'1': 1}}
meld_dict -= norm_dict # a.k.a. meld_dict.subtract(norm_dict)
meld_dict == meld_res
