AttributeError: 'NoneType' object has no attribute 'keys' (Python)-CodePudding

I'm writing a function that takes a number of dictionaries (keys - letters, values - numbers) and combines them into one dictionary. Dict values should be summarized in case of identical keys, but alwayw recieve the error for the line with " if k in d.keys():" AttributeError: 'NoneType' object has no attribute 'keys'

def combine(*args):
    d = args[0]

    for dct in args[1:]:
        for k, v in dct.items():
            if k in d.keys():
                d[k] = d[k]   v
        d = d.update(dct)
    print(d)


dict_1 = {'a': 100, 'b': 200}
dict_2 = {'a': 200, 'c': 300}
dict_3 = {'a': 300, 'd': 100}

combine_dicts(dict_1, dict_2, dict_3)

result should be {'a': 600, 'b': 200, 'c': 300, 'd': 100}

CodePudding user response：

I found the answer) since dictionaries are mutable are should've used d.update() instead of d = d.update(). And one else mistake, but not according to the question topic

CodePudding user response：

It looks like you want to accumulate values from the other two dicts into the first one, or just transfer values if not already present.

This is the code you want:

def combine(*args):
    d = args[0]
    for dct in args[1:]:
        for k, v in dct.items():
            if k in d.keys():
                d[k] = d[k]   v
            else:
                d[k] = v
        
    print(d)


dict_1 = {'a': 100, 'b': 200}
dict_2 = {'a': 200, 'c': 300}
dict_3 = {'a': 300, 'd': 100}

combine(dict_1, dict_2, dict_3)

Output as requested

CodePudding user response：

What's wrong with your code.
1. d = d.update(dct) will override exist data and and that's where you are getting AttributeError: because a none is returned. 2. You are calling a wrong function, your function is called combine and you are calling combine_dicts.

This is one of the appropriate approaches you can take you can taking using defaultdict from collections.

from collections import defaultdict

def combine(*args):
    d = defaultdict(int)
    for dct in args:
        for key, value in dct.items():
            d[key]  = value
    print(dict(d))

dict_1 = {'a': 100, 'b': 200}
dict_2 = {'a': 200, 'c': 300}
dict_3 = {'a': 300, 'd': 100}

combine(dict_1, dict_2, dict_3)

{'a': 600, 'b': 200, 'c': 300, 'd': 100}