👀 Views: 28 💬 Answers: 1 📅 Created: 2025-06-21

python dictionaries merge update Python

I'm maintaining legacy code that I'm collaborating on a project where After trying multiple solutions online, I still can't figure this out... I'm sure I'm missing something obvious here, but I'm working with an scenario when trying to merge two dictionaries in Python 3.9 that have overlapping keys. I expected the values from the second dictionary to overwrite those in the first, but I'm seeing some unexpected behavior depending on how I perform the merge. Here's the code I've been using: ```python dict1 = {'a': 1, 'b': 2, 'c': 3} dict2 = {'b': 4, 'c': 5, 'd': 6} merged_dict = {**dict1, **dict2} print(merged_dict) ``` The output is: ``` {'a': 1, 'b': 4, 'c': 5, 'd': 6} ``` This is what I expected. However, when I try merging using the `update` method like this: ```python dict1 = {'a': 1, 'b': 2, 'c': 3} dict2 = {'b': 4, 'c': 5, 'd': 6} dict1.update(dict2) print(dict1) ``` The output is: ``` {'a': 1, 'b': 4, 'c': 5} ``` I'm confused because I thought `update` would also overwrite the original dictionary with the new values, but it seems to be modifying `dict1` directly. I was under the impression that any operation that merges two dictionaries would yield the same result, but it looks like I'm missing something about how these methods interact with the dictionaries. Is there a recommended approach to merge dictionaries in Python, preserving the original when needed? Are there any best practices for handling situations like this? My development environment is Ubuntu. Am I missing something obvious? For context: I'm using Python on macOS. What am I doing wrong? What am I doing wrong?