#60MediumDictionaries & Sets· Nested Dictionaries

Dictionary Deep Merge

Applications often combine a default configuration with a user's overrides. A shallow `{**base, **override}` replaces whole nested sections; a deep merge combines them. Write `deep_merge(base, override)` that returns a new dictionary: - Start from the keys of `base`, in their order. - For each key of `override`: if both dictionaries hold a dictionary under that key, merge those two recursively; otherwise the value from `override` replaces (or adds) the key. Lists are replaced, not combined. - New keys from `override` are added after the existing ones, in `override`'s order. Neither input may be modified.

Input format

`base`, `override`: dictionaries with string keys; values are numbers, strings, booleans, lists, null or nested dictionaries.

Output format

The merged dictionary.

Examples

Input: base = {"theme":"light","editor":{"font":14,"tabs":4}}, override = {"editor":{"font":16}}

Output: {"theme":"light","editor":{"font":16,"tabs":4}}

`editor` is a dictionary on both sides, so only `font` changes and `tabs` survives.

Input: base = {"plugins":["git","lint"],"debug":false}, override = {"plugins":["format"],"port":8080}

Output: {"plugins":["format"],"debug":false,"port":8080}

Lists are replaced, and `port` is a new key added at the end.

Constraints

Nesting depth <= 10
Total number of keys <= 1000

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Dictionaries and Sets in Python

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