How can I concatenate dicts (values to values of the same key and new key)? [duplicate]

Question

I have a problem with concatenating dictionaries. Have so much code so I show in example what my problem is.

d1 = {'the':3, 'fine':4, 'word':2}
+
d2 = {'the':2, 'fine':4, 'word':1, 'knight':1, 'orange':1}
+
d3 = {'the':5, 'fine':8, 'word':3, 'sequel':1, 'jimbo':1}
=
finald = {'the':10, 'fine':16, 'word':6, 'knight':1, 'orange':1, 'sequel':1, 'jimbo':1}

It is prepering wordcounts for wordcloud. I dont know how to concatenate values of the keys it is puzzle for me. Please help. Best regards

Isidora

Welcome to Stack Overflow! Please review How to Ask and show us what you've tried! – Colloquy

Answer 1

I would use a Counter from collections for this.

from collections import Counter

d1 = {'the':3, 'fine':4, 'word':2}
d2 = {'the':2, 'fine':4, 'word':1, 'knight':1, 'orange':1}
d3 = {'the':5, 'fine':8, 'word':3, 'sequel':1, 'jimbo':1}

c = Counter()
for d in (d1, d2, d3):
    c.update(d)
print(c)

Outputs:

Counter({'fine': 16, 'the': 10, 'word': 6, 'orange': 1, 'jimbo': 1, 'sequel': 1, 'knight': 1})

Criss

Counters seems to solve a lot of dict questions these days! For this problem I would do reduce(lambda x,y:Counter(x)+Counter(y),[d1,d2, d3]) . Is update() quicker/better than adding the counters? – Stifle

@Stifle Probably not by much, if at all, and reduce is deprecated in python 3. I had originally written this with map(c.update, (d1, d2, d3)) but then I my inner functional programmer refused to allow me to abuse side effects like that. – Criss

Answer 2

import itertools

d1 = {'the':3, 'fine':4, 'word':2}
d2 = {'the':2, 'fine':4, 'word':1, 'knight':1, 'orange':1}
d3 = {'the':5, 'fine':8, 'word':3, 'sequel':1, 'jimbo':1}
dicts = [d1, d2, d3]

In [31]: answer = {k:sum(d[k] if k in d else 0 for d in dicts) for k in itertools.chain.from_iterable(dicts)}

In [32]: answer
Out[32]: 
{'sequel': 1,
 'the': 10,
 'fine': 16,
 'jimbo': 1,
 'word': 6,
 'orange': 1,
 'knight': 1}

Mayor

what about 'knight', 'sequel', 'orange', and 'jimbo'? – Mesotron

@InspectorGadget well done! – Mesotron

omg thanks nice oneliner :) – Isidora

Why the downvote? – Mayor

Answer 3

def sumDicts(*dicts):
    summed = {}
    for subdict in dicts:
        for (key, value) in subdict.items():
            summed[key] = summed.get(key, 0) + value
    return summed

Shell example:

>>> d1 = {'the':3, 'fine':4, 'word':2}
>>> d2 = {'the':2, 'fine':4, 'word':1, 'knight':1, 'orange':1}
>>> d3 = {'the':5, 'fine':8, 'word':3, 'sequel':1, 'jimbo':1}
>>> sumDicts(d1, d2, d3)
{'orange': 1, 'the': 10, 'fine': 16, 'jimbo': 1, 'word': 6, 'knight': 1, 'sequel': 1}

Mesotron

if key in summed... would probably be better off as summed[key] = summed.get(key, 0) + value – Millymilman

@SeanMcSomething that does not work on my computer... says "can't assign to function call" – Mesotron

Sorry, got some things mixed up. Fixed in edit. – Millymilman

@SeanMcSomething fixed! – Mesotron