[Python] How can I flatten a deeply nested dictionary with dot notation in Python?

I'm trying to flatten a nested dictionary in Python where the depth is not fixed. The goal is to convert it into a single-level dictionary using dot notation to represent the nested keys.

Input:

nested_dict = {
'a': {
'b': {
'c': 1
},
'd': 2
},
'e': 3
}


This is the output I want:

{
'a.b.c': 1,
'a.d': 2,
'e': 3
}


I’ve tried a recursive approach, but it gets messy with deeper levels, and I’m not sure it handles all edge cases properly. I’d appreciate a clean and efficient way to achieve this—ideally something that works regardless of how deeply the dictionary is nested.

def flatten_dict(d, parent_key='', sep='.'):
items = {}
for k, v in d.items():
new_key = f"{parent_key}{sep}{k}" if parent_key else k
if isinstance(v, dict):
items.update(flatten_dict(v, new_key, sep=sep))
else:
items[new_key] = v
return items

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