pydbg.py

"""pydbg is an implementation of the Rust builtin `dbg!` for Python."""

import inspect
import sys
import typing


__version__ = "0.3.0"


_ExpType = typing.TypeVar('_ExpType')


def dbg(exp: _ExpType) -> _ExpType:
    """Call dbg with any variable or expression.

    Calling dbg will print to stderr the current filename and lineno,
    as well as the passed expression and what the expression evaluates to:

        from pydbg import dbg

        a = 2
        b = 5

        dbg(a+b)

        def square(x: int) -> int:
            return x * x

        dbg(square(a))

    """

    for frame in inspect.stack():
        line = frame.code_context[0]
        if "dbg" in line:
            start = line.find('(') + 1
            end =  line.rfind(')')
            if end == -1:
                end = len(line)
            print(
                f"[{frame.filename}:{frame.lineno}] {line[start:end]} = {exp!r}",
                file=sys.stderr,
            )
            break

    return exp