def zodiac_compatibility(user_sign, friend_sign):
    """ Using comparison operators and conditionals, returns a given compatibility message.  
    
        Parameters
        ----------
        user_sign : str
            The user's zodiac sign as determined by their birthday input.      
        friend_sign : str
            The friend's zodiac sign as determined by their birthday input.
        Returns
        -------
        message : str
            Prints a string about friendship compatibility, changing depending on 
            whether the friends have the same signs or not."""
    
    if user_sign == friend_sign:
        message = "The stars say: you are best friends!"
        return message
    elif user_sign != friend_sign:
        message = "You get along quite well!"
        return message