Logging

Function entry/exit print logging

Every def / async def / method you write or edit gets an entry print and an exit print. No function is exempt — not private _helpers, not one-line functions, not the thin public entrypoint, not functions with no parameters. Only lambda expressions are exempt.

1. Entry print — the first statement in the body. print every incoming parameter's actual name and value, including optional parameters whose value is None; one print listing every real name is enough. "First statement" is literal: no parse call, validation, global, or dispatch runs before it. A docstring is not a statement — keep it and put the print directly after it.

   def run_todo(command):
       """Execute a todo command.
   
       Parameters: command - raw command text.
   
       Returns: the formatted result.
       """
       print(f"command={command}")        # entry print comes first
       operation, arguments = _parse_command(command)
   

   Failures: printing only after parsed = _parse_command(command); omitting a named parameter because it is unused or None; a generic label (input=, args=, params=) or one unlabeled tuple standing in for the real names. A helper that prints command= does not cover the entrypoint — every function prints its own parameters. With no parameters you still write an entry print: print("entry") or print("parameters=none").

2. Exit print — just before each return (or before falling off the end with an implicit None), print the value about to leave the function. print(result) is enough; a return= label is not required. Print everything the return hands back: for return result, [] the value is the whole tuple, so write print(result, []). Every return gets its own exit print, including an early or empty-input branch.

An exit print never substitutes for the entry print: print(result); return result alone leaves the function missing its entry print. Before finishing a function, check it top to bottom — first statement is a print, last statement before each return is a print.

Nothing is required before a raise / exception exit — only normal return paths. Use the built-in print(...) only: no log files, no logging import, no custom logger helper.