utils.py 文件源码

def number_of_args(fn):
    """Return the number of positional arguments for a function, or None if the number is variable.
    Looks inside any decorated functions."""
    try:
        if hasattr(fn, '__wrapped__'):
            return number_of_args(fn.__wrapped__)
        if any(p.kind == p.VAR_POSITIONAL for p in signature(fn).parameters.values()):
            return None
        else:
            return sum(p.kind in (p.POSITIONAL_ONLY, p.POSITIONAL_OR_KEYWORD) for p in signature(fn).parameters.values())
    except ValueError:
        # signatures don't work for built-in operators, so check for a few explicitly
        UNARY_OPS = [len, op.not_, op.truth, op.abs, op.index, op.inv, op.invert, op.neg, op.pos]
        BINARY_OPS = [op.lt, op.le, op.gt, op.ge, op.eq, op.ne, op.is_, op.is_not, op.add, op.and_, op.floordiv, op.lshift, op.mod, op.mul, op.or_, op.pow, op.rshift, op.sub, op.truediv, op.xor, op.concat, op.contains, op.countOf, op.delitem, op.getitem, op.indexOf]
        TERNARY_OPS = [op.setitem]
        if fn in UNARY_OPS:
            return 1
        elif fn in BINARY_OPS:
            return 2
        elif fn in TERNARY_OPS:
            return 3
        else:
            raise NotImplementedError("Bult-in operator {} not supported".format(fn))