change_list.html

{% extends "admin/change_list.html" %}
{% load i18n %}

{% block object-tools %}
    <ul class="object-tools" style="margin-right: 150px">
        <li>
            <a href="{{ export_url }}" class="addlink" target="_blank">{% blocktrans with cl.opts.verbose_name as name %}Exportar {{ name }}{% endblocktrans %}</a>
        </li>
    </ul>
    {{ block.super }}
{% endblock object-tools %}

export_csv.py

class ExportCsvMixin(object):
    csv_fields = None
    csv_urlname = None
    csv_filename = 'export'

    def __init__(self, *args, **kwargs):
        if not self.csv_fields or not self.csv_urlname:
            raise ValueError(_(u'A list of fields for the csv and an urlname for this action must be defined.'))
        
        super(ExportCsvMixin, self).__init__(*args, **kwargs)

    def _get_model_field(self, name, model=None):
        """
        Obtain the field of a model based on its name

        name -- name of the field
        model -- model on where to get the field
        """
        if not model:
            model = self.model

        try:
            value = model._meta.get_field(name).verbose_name
            if not isinstance(value, str) and not isinstance(value, unicode):
                value = value._proxy____unicode_cast()
        except FieldDoesNotExist:
            value = '-'

        return value

    def _get_instance_value(self, instance, attr):
        """
        Get the value of an attribute of the instance

        instance -- an instance of the model
        attr -- the attribute to which retrieve a value
        """
        value = getattr(instance, attr)

        if callable(value):
            value = value()
        
        if not value:
            value = '-'
        
        return u'%s' % value

    def _get_instance_values(self, instance, attrs):
        """
        Get the values of a attributes list of the instance

        instance -- an instance of the model
        attrs -- a list of attributes for which to obtain values
        """
        return [self._get_instance_value(instance, attr) for attr in attrs]

    def export_csv(self, request):
        """
        Create a csv file and return it as a HttResponse

        request -- a HttpResponse
        """
        objs = self.model.objects.all().select_related()

        rows = []
        for obj in objs:
            row = []
            row.extend(self._get_instance_values(obj, self.csv_fields))

            rows.append(','.join(row))

        row = []
        [row.append(self._get_model_field(attr)) for attr in self.csv_fields]
        rows.insert(0, ','.join(row))

        csv = '\r\n'.join(rows)
        csv = csv.encode('iso-8859-1')

        response = HttpResponse(csv, mimetype='text/csv')
        response['Content-Disposition'] = 'attachment; filename=%s.csv' % self.csv_filename

        return response

    def get_urls(self):
        """
        Override the get_urls method from ModelAdmin adding the export_subscriptions url
        """
        original_urls = super(ExportCsvMixin, self).get_urls()
        new_urls = patterns('',
            url(r'export/$', self.admin_site.admin_view(self.export_csv), name=self.csv_urlname)
        )

        return new_urls + original_urls
    
    def changelist_view(self, request, extra_context=None):
        """
        Pass the url for export this csv on the extra_context parameter for the changelist
        """
        if extra_context:
            extra_context.update({ 'export_url': reverse('admin:%s' % self.csv_urlname) })
        else:
            extra_context = { 'export_url': reverse('admin:%s' % self.csv_urlname) }

        return super(ExportCsvMixin, self).changelist_view(request, extra_context)

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 João Paulo Dubas <http://aval.io>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.