import re


def string_is_number(target_str):
    """ Check whether passed string can accurately be converted to a number.

    Args:
        target_str (str): string to validate if parsable to number.

    Returns:
        bool
    """
    if target_str is None:
        return False
    else:
        return bool(re.fullmatch('^\\d+$', re.sub('[^0-9]', '', target_str)))