CODEWITHSUNDEEP
pythondictionary
TeeKay
TeeKay

Reputation: 1065

Add a dictionary as a value to another dictionary with the same key

I have a dictionary like the following - 

parent_key : {child : 1, child :2}

I have another dictionary with the same format - 

parent_key : {child : 3, child :2}

Both have the same parent key and same child keys.I need to get the output like the following - 

parent_key : {{child : 1, child :2},{child : 3, child :2}}

If I use update() method, it simply updates the keys with the latest value but I need in the format I specified. Kindly help!

Upvotes: 0

Views: 215

Answers (2)

RoadRunner
RoadRunner

Reputation: 26315

Your output represents a set of dictionaries:

parent_key : {{child : 1, child :2},{child : 3, child :2}}

which is invalid. I'm also assuming those are not actually duplicate keys and you just replaced every key with child. Otherwise, the final result is even more invalid, since dictionaries can't have duplicate keys.

Instead, I suggest creating this structure instead:

{parent_key : [{child1 : 1, child2 :2}, {child1 : 3, child2 :2}]}

Which collects each inner child dictionary into a list, which seems to be closest to what you were trying to achieve.

Demo:

from collections import defaultdict

d1 = {"a": {"b": 1, "c": 2}}
d2 = {"a": {"b": 3, "c": 2}}

final_d = defaultdict(list)
for d in (d1, d2):
    for k, v in d.items():
        final_d[k].append(v)

print(final_d)
# defaultdict(<class 'list'>, {'a': [{'b': 1, 'c': 2}, {'b': 3, 'c': 2}]})

print(dict(d))
# {'a': [{'b': 1, 'c': 2}, {'b': 3, 'c': 2}]}

The above uses a collections.defaultdict of lists to aggregate the dictionaries into a list.

You could also achieve a nested dictionary result like this:

{parent_key : {child1: [1, 3], child2: [2, 2]}}

Demo:

from collections import defaultdict

d1 = {"a": {"b": 1, "c": 2}}
d2 = {"a": {"b": 3, "c": 2}}

final_d = defaultdict(lambda: defaultdict(list))

for d in (d1, d2):
    for k1, v1 in d.items():
        for k2, v2 in v1.items():
            final_d[k1][k2].append(v2)

print(final_d)
# {'a': defaultdict(<class 'list'>, {'b': [1, 3], 'c': [2, 2]})}

print({k: dict(v) for k, v in final_d.items()})
# {'a': {'b': [1, 3], 'c': [2, 2]}}

Note: defaultdict is a subclass of dict, so it acts as a normal dictionary. I've just printed two versions with defaultdict and without for convenience.

Upvotes: 1

Rafael Zerbini
Rafael Zerbini

Reputation: 141

You can do like this: 

dic_arr = [{'a' : 2, 'b' : 4, 'c' : 6},  
             {'a' : 5, 'b' : 7, 'c' : 8}, 
             {'d' : 10}] 

res = {} 
for sub in dic_arr: 
    for key, val in sub.items():  
        res.setdefault(key, []).append(val) 

print(str(res))

Upvotes: 0

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