Question

I have a problem with Django.

My error message:

UnboundLocalError at /city/city
local variable ‘adv_city’ referenced before assignment

Traceback: http://dpaste.com/751727/

views:

def advert_by_city(request):
    c = request.GET.get('city', '')
    if c:
        adv_city = Advert.objects.filter(city=c)

    adverts = Advert.objects.values('city').distinct()
    return render_to_response('advert_by_city', {'adverts':adverts},{'adv_city':adv_city}, context_instance=RequestContext(request))

template:

{% for city in adverts %}
    <a href="city?{{ city.city }}"/>{{city.city}}</a>
<br/>
{% endfor %}

{% for adverts in adv_city%}
    {{adverts.title}}
{% endfor%}

model:

class Advert(models.Model):

    title = models.CharField(max_length=255)
    city = models.CharField(max_length=255)

How to fix it?

Answer 1

You should give a default value for adv_city in case c evaluates to false. For instance, an empty list might work in your case:

c = request.GET.get('city', '')
adv_city = Advert.objects.filter(city=c) if c else []

If you don’t do that, and c is false (Python treats the empty string as false, as you may know), then the adv_city variable will not be considered assigned.

If you can have a valid Advert with an empty string as the city attribute, then just remove the if and let the filter run for any value of c.