How to Efficiently Extract All Occurrences of a Key in Nested Dictionaries and Lists?

How to find all occurrences of a key in nested dictionaries and lists

Traversing complex data structures to extract specific values can be a common challenge in programming. This article addresses the problem of finding all occurrences of a particular key within a deeply nested dictionary and list structure, providing a detailed solution and performance analysis.

Consider a sample dictionary consisting of nested lists and dictionaries, similar to:

{
    "id": "abcde",
    "key1": "blah",
    "key2": "blah blah",
    "nestedlist": [
        {
            "id": "qwerty",
            "nestednestedlist": [
                {
                    "id": "xyz",
                    "keyA": "blah blah blah"
                },
                {
                    "id": "fghi",
                    "keyZ": "blah blah blah"
                }
            ],
            "anothernestednestedlist": [
                {
                    "id": "asdf",
                    "keyQ": "blah blah"
                },
                {
                    "id": "yuiop",
                    "keyW": "blah"
                }
            ]
        }
    ]
}

The goal is to extract all values of the "id" key from this structure, resulting in a list like:

["abcde", "qwerty", "xyz", "fghi", "asdf", "yuiop"]

To achieve this, various approaches have been suggested, including:

1. gen_dict_extract: A recursive function that checks for dictionaries, lists, and strings, yielding the value when the key matches. (Fastest and recommended)
2. find_all_items: A similar recursive function that works specifically for dictionaries.
3. findkeys: A function that recursively searches for keys by iterating through the dictionary.
4. get_recursively: A generic function for extracting values using recursion.
5. find: A concise recursive function similar to get_recursively.
6. dict_extract: A function that traverses the structure using nested loops, checking for dictionaries and lists.

Performance analysis reveals that the gen_dict_extract function outperforms the others in terms of speed, while ensuring reliability and support for various data types within the structure.

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