utils.py

import inspect

from collections import namedtuple


def signature(f):
    r"""Get the function f 's input arguments. A useful gadget
    when some function slot might be instantiated into multiple functions.

    Args:
        f (:obj:`function`) : the function to get the input arguments.

    Returns:
        namedtuple : of args, default, varargs, keywords, respectively.s

    """
    sig = inspect.signature(f)
    args = [
        p.name for p in sig.parameters.values()
        if p.kind == inspect.Parameter.POSITIONAL_OR_KEYWORD
    ]
    varargs = [
        p.name for p in sig.parameters.values()
        if p.kind == inspect.Parameter.VAR_POSITIONAL
    ]
    varargs = varargs[0] if varargs else None
    keywords = [
        p.name for p in sig.parameters.values()
        if p.kind == inspect.Parameter.VAR_KEYWORD
    ]
    keywords = keywords[0] if keywords else None
    defaults = [
                   p.default for p in sig.parameters.values()
                   if p.kind == inspect.Parameter.POSITIONAL_OR_KEYWORD
                      and p.default is not p.empty
               ] or None
    argspec = namedtuple('Signature', ['args', 'defaults', 'varargs', 'keywords'])
    return argspec(args, defaults, varargs, keywords)