url patterns

there are cases when certain views take optional parameters. often times these are provided within the url generator funtion. for example, when using django’s authentication login view:

def login(request, template_name=’registration/login.html’,

redirect_field_name=REDIRECT_FIELD_NAME, authentication_form=AuthenticationForm, current_app=None, extra_context=None):

the url generator function looks like this:

url(r’^login/$’,

‘django.contrib.auth.views.login’, {

‘template_name’:’registration/login.html’, ‘authentication_form’:EmailAuthenticationForm

}, name=”login”),

however, it is possible also to provide optional parameters within the url pattern itself using this format:

(?:/(?P<sport>[a-z\s]*))?

explaination: the outer grouping ()? is the regex pattern for optional. however, the ?: is necessary to capture the sub-expression enclosed by the commonly used (?P<name>) expression.

These two patterns can combined:

url(r’^t/(?P<slug>[A-Za-z][a-zA-Z0-9-]+?)/$, OrganizationView.as_view(), name=”organization”), url(r’^t/(?P<slug>[A-Za-z][a-zA-Z0-9-]+?)/(?P<sport>[a-zs]*)/$’, OrganizationView.as_view(), name=”organization-with-sports”),

into:

url(r’^t/(?P<slug>[A-Za-z][a-zA-Z0-9-]+?)(?:/(?P<sport>[a-zs]*))?/connects(?:/(?P<year>[0-9]{4}))?/?$’, OrganizationView.as_view(), name=”organization”),

which elimintes duplicate code (DRY) and tracking two different url name resolutions:

from django.core.urlresolvers import

url(r’^t/(?P<slug>[A-Za-z][a-zA-Z0-9-]+?)(?:/(?P<sport>[a-zs]*))?/connects(?:/(?P<year>[0-9]{4}))?/?$’, OrganizationView.as_view(), {‘root’:’connects’}, name=”connections-team”),