How To Combine Multiple Dicts, Summing The Values Of Common Keys (and Retaining Those With Value 0) In Python?

Given three dicts d1, d2 and d3: d1 {'a':1,'b':2,'c':3, 'd':0) d2 {'b':76} d3 {'a': 45, 'c':0} There are some key names that are common to more than one dict (and in reality, th

Solution 1:

You could use update instead of + with Counter if you want the 0 keys to persist:

>>>c = Counter()>>>for d in d1, d2, d3:...    c.update(d)...>>>c
Counter({'b': 78, 'a': 46, 'c': 3, 'd': 0})

(This is probably a dup, but I can't find it right now.)

Solution 2:

collections.defaultdict to the rescue

importcollectionsd= collections.defaultdict(int)
for thing in [d1, d2, d3]:
    for k, v in thing.items():
        d[k] += v

Solution 3:

UNTESTED:

defmerge_dicts(*dicts):
    res = {}
    for key inset(sum(map(list, dicts), [])):
        res[key] = 0for dct in dicts:
            res[key] += dct.get(key, 0)
    return res

Example usage:

merge_dicts(d1, d2, d3)