Why can we “from sqlalchemy import insert” when it is defined in “sql.alchemy.sql.expression”?

I recently saw a document on https://docs.sqlalchemy.org/en/14/core/dml.html#sqlalchemy.sql.expression.insert.

I want to know why insert() is declared under sqlalchemy.sql.expression, and we can still import it by from sqlalchemy import insert.

Answer

It’s defined here: https://github.com/sqlalchemy/sqlalchemy/blob/master/lib/sqlalchemy/__init__.py#L53

__init__.py is a file that runs automatically whenever the folder is imported in Python.