👀 Views: 0 💬 Answers: 1 📅 Created: 2025-06-13

python dictionaries merging Python

I'm confused about I'm building a feature where I've searched everywhere and can't find a clear answer... I'm trying to merge two dictionaries in Python 3.10, but I'm running into problems where keys get overwritten rather than preserving their values. I have two dictionaries: ```python dict_a = {'a': 1, 'b': 2, 'c': 3} dict_b = {'b': 3, 'c': 4, 'd': 5} ``` When I use the following method to merge them: ```python merged_dict = {**dict_a, **dict_b} ``` I expect `merged_dict` to contain: ```python {'a': 1, 'b': 3, 'c': 4, 'd': 5} ``` However, I noticed that `dict_a` values are getting overwritten by `dict_b` values, which is expected behavior. But I need a way to combine these dictionaries while preserving the values from both dictionaries in cases where the keys overlap. I've also considered using a defaultdict to accumulate values, but I'm not sure how to structure it properly: ```python from collections import defaultdict result = defaultdict(list) for d in (dict_a, dict_b): for key, value in d.items(): result[key].append(value) ``` This seems to allow me to preserve values, but the final structure ends up looking like this: ```python {'a': [1], 'b': [2, 3], 'c': [3, 4], 'd': [5]} ``` While this does store all values, I would prefer a single value per key (like the maximum or minimum from the lists). What would be the best approach to merge these dictionaries in a way that allows me to specify how to handle duplicate keys? Any suggestions or best practices would be greatly appreciated. I'm using Python 3.10.0 with no special libraries beyond the standard library. Hoping someone can shed some light on this. My development environment is Ubuntu 20.04. Hoping someone can shed some light on this.