69 lines
2.2 KiB
Python
69 lines
2.2 KiB
Python
# echo.py: Tracing function calls using Python decorators.
|
|
#
|
|
# Written by Thomas Guest <tag@wordaligned.org>
|
|
# Please see http://wordaligned.org/articles/echo
|
|
#
|
|
# Place into the public domain.
|
|
|
|
"""Echo calls made to functions in a module.
|
|
|
|
"Echoing" a function call means printing out the name of the function
|
|
and the values of its arguments before making the call (which is more
|
|
commonly referred to as "tracing", but Python already has a trace module).
|
|
|
|
Alternatively, echo.echo can be used to decorate functions. Calls to the
|
|
decorated function will be echoed.
|
|
|
|
Example:
|
|
-------
|
|
|
|
@echo.echo
|
|
def my_function(args):
|
|
pass
|
|
|
|
"""
|
|
|
|
from __future__ import annotations
|
|
|
|
import functools
|
|
import sys
|
|
from typing import TYPE_CHECKING
|
|
|
|
if TYPE_CHECKING:
|
|
from typing import Any, Callable
|
|
|
|
|
|
def format_arg_value(arg_val: tuple[str, tuple[Any, ...]]) -> str:
|
|
"""Return a string representing a (name, value) pair."""
|
|
arg, val = arg_val
|
|
return f"{arg}={val!r}"
|
|
|
|
|
|
def echo(fn: Callable, write: Callable[[str], int | None] = sys.stdout.write) -> Callable:
|
|
"""Echo calls to a function.
|
|
|
|
Returns a decorated version of the input function which "echoes" calls
|
|
made to it by writing out the function's name and the arguments it was
|
|
called with.
|
|
"""
|
|
# Unpack function's arg count, arg names, arg defaults
|
|
code = fn.__code__
|
|
argcount = code.co_argcount
|
|
argnames = code.co_varnames[:argcount]
|
|
fn_defaults: tuple[Any] = fn.__defaults__ or ()
|
|
argdefs = dict(list(zip(argnames[-len(fn_defaults) :], fn_defaults)))
|
|
|
|
@functools.wraps(fn)
|
|
def wrapped(*v: Any, **k: Any) -> Callable:
|
|
# Collect function arguments by chaining together positional,
|
|
# defaulted, extra positional and keyword arguments.
|
|
positional = list(map(format_arg_value, list(zip(argnames, v))))
|
|
defaulted = [format_arg_value((a, argdefs[a])) for a in argnames[len(v) :] if a not in k]
|
|
nameless = list(map(repr, v[argcount:]))
|
|
keyword = list(map(format_arg_value, list(k.items())))
|
|
args = positional + defaulted + nameless + keyword
|
|
write(f"{fn.__name__}({', '.join(args)})\n")
|
|
return fn(*v, **k)
|
|
|
|
return wrapped
|