Django reverse causing url circular import, why?

Question

I get this error:

The included urlconf 'fouraxis.urls' does not appear to have any patterns in it. If you see valid patterns in the file then the issue is probably caused by a circular import.

I know the url pattern has something in it, it looks like this:

from django.conf.urls import include, url
from django.contrib import admin

    urlpatterns = [
        url(r'^perfil/', include('clientes.urls'), namespace="cliente"),
        url(r'^admin/', include(admin.site.urls))
    ]

clientes.urls:

from django.conf.urls import url
from django.contrib.auth import views as auth_views

from clientes import views

urlpatterns = [
        # login
        url(r'^login/$', auth_views.login, {'template_name': 'perfiles/login.html'}, name="login"),
        url(r'^logout/$', auth_views.logout, {'template_name': 'perfiles/logged_out.html'}, name="login"),

        url(r'^mi_perfil/$', views.mi_perfil, name="mi_perfil"),
        url(r'^registro_usuario/$', views.RegistroUsuario.as_view(), name="registro_usuario")
    ]

The RegistroUsuario view looks like this:

class RegistroUsuario(FormView):
    template_name = "perfiles/registro_usuario.html"
    form_class = UserCreationForm
    success_url = reverse("cliente:mi_perfil")  # THIS REVERSE

    def form_valid(self, form):
        return redirect("cliente:mi_perfil")

    context = {'form': UserCreationForm}

I understand I can replace the reverse with a plain-text url like this perfil/mi_perfil. But, I want to know why is this happening with reverse, I can't find the explanation on de docs. Also, using reverse is better cause it is dynamic (if anytime I change the url, it still works as long as it keeps its name).

Answer 1

The reverse() call is made when the view is imported, which is probably when the urlconf is first loaded. You need to use reverse_lazy() instead:

from django.core.urlresolvers import reverse_lazy

class RegistroUsuario(FormView):
    template_name = "perfiles/registro_usuario.html"
    form_class = UserCreationForm
    success_url = reverse_lazy("cliente:mi_perfil")  # THIS REVERSE

    def form_valid(self, form):
        return redirect("cliente:mi_perfil")

    context = {'form': UserCreationForm}