Filtering a dictionary of dictionaries by a value

Question

I have a small example of a nested dictionary (in my case a collections defaultdict):

all_dict = {'d1': {'a': 2, 'b': 4, 'c': 10}, 
            'd2': {'a': 1, 'b': 23,'c': 0},
            'd3': {'a': 4, 'b': 12,'c': 4},
            'd4': {'a': 0, 'b': 4, 'c': 3},
            'd5': {'a': 4, 'b': 0, 'c': 1}}

And I would like to filter all the zero values in all_dict. In my real data, the nested dictionaries are very big. I would like any general "pythonic" solution. I tried some comprehension but I failed. I would like some like:

all_dict_filtered = 
           {'d1': {'a': 2, 'b': 4, 'c': 10}, 
            'd2': {'a': 1, 'b': 23},
            'd3': {'a': 4, 'b': 12,'c': 4},
            'd4': {'b': 4, 'c': 3},
            'd5': {'a': 4, 'c': 1}}

Any tip would be great. Thank you for your time and attention. Paulo

I have this but is ugly:

    filtered = defaultdict(dict)
    for k1, v1 in all_dict.items():
        for k2, v2 in v1.items():
            if v2 > 0:
                filtered[k1] = filtered.get(k1, {})
                filtered[k1][k2] = v2
defaultdict(dict,
            {'d1': {'a': 2, 'b': 4, 'c': 10},
             'd2': {'a': 1, 'b': 23},
             'd3': {'a': 4, 'b': 12, 'c': 4},
             'd4': {'b': 4, 'c': 3},
             'd5': {'a': 4, 'c': 1}})

Answer 1

Simple one-liner using dict comprehensions:

import pprint

all_dict = {
    'd1': {'a': 2, 'b': 4, 'c': 10},
    'd2': {'a': 1, 'b': 23, 'c': 0},
    'd3': {'a': 4, 'b': 12, 'c': 4},
    'd4': {'a': 0, 'b': 4, 'c': 3},
    'd5': {'a': 4, 'b': 0, 'c': 1}
}

pprint.pprint({k: {key: value for key, value in v.items() if value != 0} for k, v in all_dict.items()})

Output:

{'d1': {'a': 2, 'b': 4, 'c': 10},
 'd2': {'a': 1, 'b': 23},
 'd3': {'a': 4, 'b': 12, 'c': 4},
 'd4': {'b': 4, 'c': 3},
 'd5': {'a': 4, 'c': 1}}