These sorts of cases are why I wrote srgn [0]. It's based on tree-sitter too. Calling it as

     cat file.py | srgn --py def --py identifiers 'database' 'db'

will replace all mentions of `database` inside identifiers inside (only!) function definitions (`def`) with `db`.

An input like

    import database
    import pytest


    @pytest.fixture()
    def test_a(database):
        return database


    def test_b(database):
        return database


    database = "database"


    class database:
        pass

is turned into

    import database
    import pytest


    @pytest.fixture()
    def test_a(db):
        return db


    def test_b(db):
        return db


    database = "database"


    class database:
        pass

which seems roughly like what the author is after. Mentions of "database" outside function definitions are not modified. That sort of logic I always found hard to replicate in basic GNU-like tools. If run without stdin, the above command runs recursively, in-place (careful with that one!).

Note: I just wrote this, and version 0.13.2 is required for the above to work.

[0]: https://github.com/alexpovel/srgn