https://philipphagenlocher.de/post/hooking-into-python-programs/

hooking.py

#!/usr/bin/env python3

import code
import ctypes
import inspect
import logging


def hook(
    banner_msg: str | None = None,
    overwrite_locals: bool = False,
    logger: str = "root",
):
    """Hooks into the caller, starting an interactive shell.

    Copies globals and locals from the caller into the shell and local
    variables from the shell will be copied back to the caller.

    Args:
        banner_msg:
            Additional message to display on shell startup
        overwrite_locals:
            If `True`, overwrites locals in the caller function with locals
            from the interactive shell
        logger:
            Name of the logger to use for reporting the hook
    """
    # Get stack frame for caller
    stack = inspect.stack()[1]
    frame = stack.frame

    # Set up log function
    def log(msg: str):
        logging.getLogger(logger).handle(
            logging.LogRecord(
                name=logger,
                level=logging.DEBUG,
                pathname=stack.filename,
                lineno=stack.lineno,
                msg=msg,
                args=None,
                exc_info=None,
                func=stack.function,
            )
        )

    # Log start of REPL
    log("Starting interactive shell.")

    # Copy locals and globals of caller's stack frame
    locals_copy = dict(frame.f_locals)
    globals_copy = dict(frame.f_globals)
    shell_locals = dict()
    shell_locals.update(globals_copy)
    shell_locals.update(locals_copy)

    # Format banner
    banner = f"Hooked at {stack.filename}:{stack.lineno} - Exit with CTRL+D"
    if banner_msg:
        banner = f"{banner_msg}\n{banner}"

    # Start interactive shell
    code.interact(banner, local=shell_locals, exitmsg="")

    # Update caller's locals with modified locals from shell
    if overwrite_locals:
        locals_to_update = dict()
        for key, value in shell_locals.items():
            if key in locals_copy:
                locals_to_update[key] = value
        frame.f_locals.update(locals_to_update)
        ctypes.pythonapi.PyFrame_LocalsToFast(ctypes.py_object(frame), ctypes.c_int(0))

    # Log exit from REPL
    log("Returned from interactive shell. Resuming execution.")

    # Delete frame to avoid cyclic references
    del stack
    del frame