import math


def is_null(val):
    """Returns True if 'val' is None, NaN, or a blank string.
    Returns False otherwise.
    """
    if val is None:
        return True

    if isinstance(val, float) and math.isnan(val):
        return True

    if isinstance(val, str) and len(val.strip())==0:
        return True

    return False