def listify(x):
    """
    Example:
        >>> listify('a b c')
        ['a', 'b', 'c']

        >>> listify('a, b, c')
        ['a', 'b', 'c']

        >>> listify(3)
        [3]
    """
    if isinstance(x, str):
        if ',' in x:
            return [x1.strip() for x1 in x.split(',')]
        else:
            return [x1 for x1 in x.split(' ') if x1]
    elif isinstance(x, list):
        return x
    elif isinstance(x, tuple) or isinstance(x, dict):
        return list(x)
    else:
        return [x]