How to Efficiently Combine Dictionaries in Python with Overlapping Keys?

How to Pythonically Combine Dictionaries with Overlapping Keys

Combining dictionaries with overlapping keys often arises in programming. Suppose we have two dictionaries:

Dict A: {'a': 1, 'b': 2, 'c': 3}
Dict B: {'b': 3, 'c': 4, 'd': 5}

We aim to create a new dictionary with the following properties:

• For keys present in both dictionaries, sum their corresponding values.
• For keys present in only one dictionary, retain their original values.

Pythonic Solution: Using Collections.Counter

One elegant and Pythonic approach employs the collections.Counter class, a subclass of dict that simplifies counting and summation tasks. Here's how to use it:

from collections import Counter

A = Counter({'a':1, 'b':2, 'c':3})
B = Counter({'b':3, 'c':4, 'd':5})

result = A + B

A B performs a counter-addition operation, resulting in a new Counter object:

Counter({'c': 7, 'b': 5, 'd': 5, 'a': 1})

This new Counter holds the desired combined values. Since Counters are derived from dicts, you can interact with them as regular dictionaries, including iterating over keys and values.

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