Calculating frequency of items in a dictionary

[scidam]

You can use dict.setdefault method, e.g.

desired_output = dict()                                                                                                                                                                                                                                                       
for item in input_dict: 
    ss = sum(v for k, v in input_dict[item].items()) 
    tt = desired_output.setdefault(ss, list()) 
    tt.append(item)