Django. Apply function to queryset

问题

I have a queryset and I want to apply function (port_to_app) to its field (dst_port). And then access it from template. How do I do that? I've read about filters and tags, but can't understand the way they work.

models.py

class FlowQuerySets(models.QuerySet):
     def top_app(self):
        return self.values('dst_port')\
            .annotate(traffic=Sum('bytes')).order_by('-traffic')[:10]

class Flow(models.Model):
    id = models.BigIntegerField(primary_key = True)
    ip_src = models.CharField(max_length=15)
    ip_dst = models.CharField(max_length=15)
    src_port = models.IntegerField()
    dst_port = models.IntegerField()

    objects = FlowQuerySets.as_manager()

    def port_to_app(self):
        "returns application instead of port using socket module"
        import socket
        if self.dst_port:
            return socket.getservbyport(int(dst_port))

views.py

def top_conversations_app(request):
    top_app = Flow.objects.top_app()
    return render (request, 'flow/home.html', {'top_app': top_app}) 

home.html

{% for p in top_app %}
            {{ p.dst_port }}
            {{ p.traffic | filesizeformat}}
{% endfor %}

回答1:

The port_to_app on the model object is not available because top_app uses .values and thus returns a list of dicts. Try adjusting your QuerySet to something like this instead:

class FlowQuerySets(models.QuerySet):
    def top_app(self):
        import socket
        for obj in self.values('dst_port')\
            .annotate(traffic=Sum('bytes')).order_by('-traffic')[:10]:
            if obj['dst_port']:
                obj['dst_port'] = socket.getservbyport(int(obj['dst_port']))
            yield obj

回答2:

well, you can mark is as a property

@property
def port_app(self):
    "returns application instead of port using socket module"
    import socket
    if self.dst_port:
        return socket.getservbyport(int(dst_port))

and then in your template you can access it as any other model property

{% for p in top_app %}
    {{ p.port_app }}
{% endfor %}

来源：https://stackoverflow.com/questions/34929761/django-apply-function-to-queryset