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30-seconds-of-code/snippets/combine-values.md
2023-04-28 22:24:23 +03:00

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---
title: Combine dictionary values
type: snippet
tags: [dictionary]
cover: fruit-feast
dateModified: 2021-04-04T14:32:35+03:00
---
Combines two or more dictionaries, creating a list of values for each key.
- Create a new `collections.defaultdict` with `list` as the default value for each key and loop over `dicts`.
- Use `dict.append()` to map the values of the dictionary to keys.
- Use `dict()` to convert the `collections.defaultdict` to a regular dictionary.
```py
from collections import defaultdict
def combine_values(*dicts):
res = defaultdict(list)
for d in dicts:
for key in d:
res[key].append(d[key])
return dict(res)
```
```py
d1 = {'a': 1, 'b': 'foo', 'c': 400}
d2 = {'a': 3, 'b': 200, 'd': 400}
combine_values(d1, d2) # {'a': [1, 3], 'b': ['foo', 200], 'c': [400], 'd': [400]}
```