def average_tweets_per_user(tweets, users_with_freq):
    
    """
    Return the average number of tweets per user from a list of tweets.

    :param tweets: the list of tweets.
    :param users_with_freq: a Counter of usernames with the number of tweets in 'tweets' from each user.

    :return: float. average number of tweets per user
    """

    tweets_number = len(tweets)
    users_number = len(users_with_freq)

    return tweets_number/users_number