python - NoReverseMatch in url in django app -

i have url , everythis should ok error.

this url:

url(r'^/(?p<genre>%s)$' % '|'.join([g.code g in genre.objects.all()]), eventlistview.as_view(), name='genre'), 

here error message:

reverse 'genre' arguments '()' , keyword arguments '{u'genre': ''}' not found. 0 pattern(s) tried: [] 

in line of html code:

<a {% if genre == view.genre %} class="active" href="{% url 'events' %}" title="{% trans 'reset filter' %}"{% else %} href="{% url 'genre' genre=genre.code %}"{% endif %}>{{ genre.name }}</a> 

my view:

class eventlistview(pagecontextmixin, listview):     model = booking     page_context_kwargs = {'selected': reverse_lazy('events')}     template_name = 'events/event_list.html'      def get_queryset(self):         filter_ = {'eventlist': true} # , 'season__in': settings.events_seasons}         self.rooms = settings.events_rooms         self.genres = list(settings.events_genres)         genre_names = dict([(g.evis_id, g.description_de) g in genre.objects.filter(evis_id__in=[g['evis_id'] g in self.genres])])         genre in self.genres:             genre['name'] = genre_names.get(genre['evis_id'], genre['name'])         if 'genre' in self.kwargs:             self.genre = [g g in self.genres                           if g['url'] == self.kwargs['genre']][0]             filter_['eventgenre__genre__evis_id'] = self.genre['evis_id']         elif 'room' in self.kwargs:             self.room = [r r in self.rooms if r['url'] == self.kwargs['room']][0]             filter_['venue_description'] = self.room['venue_description']         return self.model.objects.filter(**filter_) 

html template:

<div id="eventlistcontainer">     {% if view.genres or view.rooms %}     <input type="checkbox" id="filteropener" class="hidden-input" />     <div class="filterwrap">         <label for="filteropener" class="filterlabel" title="{% trans "toggle filter" %}">{% trans "filter" %}</label>         {% if view.genre or view.room %}         <span class="filtertag">             : <b>{% if view.genre %}{{ view.genre.name }}{% else %}{{ view.room.name }}{% endif %}</b>         </span>         <a class="filterreset" href="{% url 'events' %}" title="{% trans 'reset filter' %}">             <img src="{{ static_url }}images/icon_close.png" alt="{% trans 'reset filter' %}" />         </a>         {% endif %}     </div>     <div class="eventfilter">         <div>             <h2>{% trans "genre" %}</h2>             <ul class="linklist list1">             {% genre in view.genres %}                 <li>                 <a {% if genre == view.genre %} class="active" href="{% url 'events' %}" title="{% trans 'reset filter' %}"{% else %} href="{% url 'genre' genre=genre.code %}"{% endif %}>{{ genre.name }}</a>                 </li>             {% if forloop.counter == 4 %}             </ul>             <ul class="linklist list2">             {% endif %}             {% endfor %}             </ul>         </div>         <div>             <h2>{% trans "concert venues" %}</h2>             <ul class="linklist list3">             {% room in view.rooms %}                 <li>                 <a {% if room == view.room %} class="active" href="{% url 'events' %}" title="{% trans "reset filter" %}"{% else %} href="{% url "room" room=room.url %}"{% endif %}>{{ room.name }}</a>                 </li>             {% if forloop.counter == 6 %}             </ul>             <ul class="linklist list4">             {% endif %}             {% endfor %}             </ul>         </div>     </div>     {% endif %}      {% object_list|sort_by_highlight_past events %}     <ul class="eventlist{% if events.0.past %} past{% endif %}">         {% event in events %}         {% ifchanged event.past %}         {% if not forloop.first %}     </ul>     <h3>vergangene veranstaltungen</h3>     <ul class="eventlist past">         {% endif %}         {% endifchanged %}         <li class="{{ event.status|default:"" }}{% if forloop.first , not event.past %} wide{% endif %}">             {% im in event.eventimage_set.all|slice:":1" %}             <a href="{{ event.get_absolute_url }}" class="image">                 {% if forloop.parentloop.first , not event.past %}                 <img src="{{ im.image.image.3.url }}" alt="{{ im.text }}" />                 {% endif %}                 <img src="{{ im.image.image.2.url }}" alt="{{ im.text }}" />             </a>             {% endfor %}             <div class="textbox">                 <a href="{{ event.get_absolute_url }}">                     <p class="date">{{ event.start|fancy_date }}</p>                     <h2>{{ event.name }}</h2>                     <p class="location">{{ event.venue_description }}</p>                 </a>                 {% if event.description_short %}                 <p class="additional-info">{{ event.description_short }}</p>                 {% endif %}                 <a href="{{ event.get_absolute_url }}" class="button">{% trans "details" %}</a>                 {% if event.status %}                 <p class="status">{% trans event.status %}!</p>                 {% elif event.selling_status_code == "ef" %}                 <a href="{{ event.get_absolute_url }}" class="button">{{ event.selling_status_description }}</a>                 {% elif event|ticket_link %}                 <a href="{{ event|ticket_link }}" class="button">{% trans "tickets" %}</a>                 {% endif %}             </div>         </li>         {% endfor %}     </ul>     {% endwith %} </div> 

genres

events_genres = (     {         'url': 'orchestermusik',         'evis_id': '1',         'name': 'orchestermusik'     },     {         'url': 'vokale-musik',         'evis_id': '2',         'name': 'vokale musik'     },) 

trying put genres in url options bad idea. apart else, query evaluated once, url accept genres had been created @ server startup.

instead, kind of thing check in view, get_object_or_404; has same result, of returning 404 if genre doesn't exist.

however, in particular case error because value of genre.code passing {% url %} tag empty reason. without seeing rest of template or view, though, can't tell why.