get_valid_slug_filename.py

def get_valid_filename(s):
    """
    Return the given string converted to a string that can be used for a clean
    filename. Remove leading and trailing spaces; convert other spaces to
    underscores; and remove anything that is not an alphanumeric, dash,
    underscore, or dot.
    # https://github.com/django/django/blob/master/django/utils/text.py
    """
    s = str(s).strip().replace(' ', '_')
    s = re.sub(r'(?u)[^-\w.]', '', s)
    return s