Define the regexp used for the search

def search_regexp(self):
        """
        Define the regexp used for the search
        """
        if ((self.season == "") and (self.episode == "")):
            regexp = '^%s.*' % self.title.lower()
        elif (self.episode == ""):
            regexp = '^%s.*(s[0]*%s|season[\s\_\-\.]*%s).*' % (self.title.lower(), self.season, self.season)
        else:
            regexp = '^%s.*((s[0]*%s.*e[0]*%s)|[0]*%sx[0]*%s).*' % (self.title.lower(), self.season, self.episode, self.season, self.episode)
        return regexp