# Django 1.8.18.dev20170123152445 documentation

# `django.core.urlresolvers` utility functions

## reverse()

If you need to use something similar to the `url` template tag in your code, Django provides the following function:

`reverse`(viewname, urlconf=None, args=None, kwargs=None, current_app=None)

`viewname` can be a string containing the Python path to the view object, a URL pattern name, or the callable view object. For example, given the following `url`:

    from news import views

    url(r'^archive/$', views.archive, name='news-archive')

you can use any of the following to reverse the URL:

    # using the named URL
    reverse('news-archive')

    # passing a callable object
    # (This is discouraged because you can't reverse namespaced views this way.)
    from news import views
    reverse(views.archive)

If the URL accepts arguments, you may pass them in `args`. For example:

    from django.core.urlresolvers import reverse

    def myview(request):
        return HttpResponseRedirect(reverse('arch-summary', args=[1945]))

You can also pass `kwargs` instead of `args`. For example:

    >>> reverse('admin:app_list', kwargs={'app_label': 'auth'})
    '/admin/auth/'

`args` and `kwargs` cannot be passed to `reverse()` at the same time.

If no match can be made, `reverse()` raises a `NoReverseMatch` exception.

The `reverse()` function can reverse a large variety of regular expression patterns for URLs, but not every possible one. The main restriction at the moment is that the pattern cannot contain alternative choices using the vertical bar (`"|"`) character. You can quite happily use such patterns for matching against incoming URLs and sending them off to views, but you cannot reverse such patterns.

The `current_app` argument allows you to provide a hint to the resolver indicating the application to which the currently executing view belongs. This `current_app` argument is used as a hint to resolve application namespaces into URLs on specific application instances, according to the namespaced URL resolution strategy.

The `urlconf` argument is the URLconf module containing the url patterns to use for reversing. By default, the root URLconf for the current thread is used.

Deprecated since version 1.8: The ability to reverse using the Python path, e.g. `reverse('news.views.archive')`, has been deprecated.

Make sure your views are all correct.

As part of working out which URL names map to which patterns, the `reverse()` function has to import all of your URLconf files and examine the name of each view. This involves importing each view function. If there are any errors whilst importing any of your view functions, it will cause `reverse()` to raise an error, even if that view function is not the one you are trying to reverse.

Make sure that any views you reference in your URLconf files exist and can be imported correctly. Do not include lines that reference views you haven’t written yet, because those views will not be importable.

Note

The string returned by `reverse()` is already urlquoted. For example:

    >>> reverse('cities', args=['Orléans'])
    '.../Orl%C3%A9ans/'

Applying further encoding (such as `urlquote()` or `urllib.quote`) to the output of `reverse()` may produce undesirable results.

## reverse_lazy()

A lazily evaluated version of reverse().

`reverse_lazy`(viewname, urlconf=None, args=None, kwargs=None, current_app=None)

It is useful for when you need to use a URL reversal before your project’s URLConf is loaded. Some common cases where this function is necessary are:

- providing a reversed URL as the `url` attribute of a generic class-based view.
- providing a reversed URL to a decorator (such as the `login_url` argument for the `django.contrib.auth.decorators.permission_required()` decorator).
- providing a reversed URL as a default value for a parameter in a function’s signature.

## resolve()

The `resolve()` function can be used for resolving URL paths to the corresponding view functions. It has the following signature:

`resolve`(path, urlconf=None)

`path` is the URL path you want to resolve. As with `reverse()`, you don’t need to worry about the `urlconf` parameter. The function returns a `ResolverMatch` object that allows you to access various meta-data about the resolved URL.

If the URL does not resolve, the function raises a `Resolver404` exception (a subclass of `Http404`) .

class `ResolverMatch`
  `func`

    The view function that would be used to serve the URL

  `args`

    The arguments that would be passed to the view function, as parsed from the URL.

  `kwargs`

    The keyword arguments that would be passed to the view function, as parsed from the URL.

  `url_name`

    The name of the URL pattern that matches the URL.

  `app_name`

    The application namespace for the URL pattern that matches the URL.

  `namespace`

    The instance namespace for the URL pattern that matches the URL.

  `namespaces`

    The list of individual namespace components in the full instance namespace for the URL pattern that matches the URL. i.e., if the namespace is `foo:bar`, then namespaces will be `['foo', 'bar']`.

  `view_name`

    The name of the view that matches the URL, including the namespace if there is one.

A `ResolverMatch` object can then be interrogated to provide information about the URL pattern that matches a URL:

    # Resolve a URL
    match = resolve('/some/path/')
    # Print the URL pattern that matches the URL
    print(match.url_name)

A `ResolverMatch` object can also be assigned to a triple:

    func, args, kwargs = resolve('/some/path/')

One possible use of `resolve()` would be to test whether a view would raise a `Http404` error before redirecting to it:

    from django.core.urlresolvers import resolve
    from django.http import HttpResponseRedirect, Http404
    from django.utils.six.moves.urllib.parse import urlparse

    def myview(request):
        next = request.META.get('HTTP_REFERER', None) or '/'
        response = HttpResponseRedirect(next)

        # modify the request and response as required, e.g. change locale
        # and set corresponding locale cookie

        view, args, kwargs = resolve(urlparse(next)[2])
        kwargs['request'] = request
        try:
            view(*args, **kwargs)
        except Http404:
            return HttpResponseRedirect('/')
        return response

## get_script_prefix()

`get_script_prefix`()

Normally, you should always use `reverse()` to define URLs within your application. However, if your application constructs part of the URL hierarchy itself, you may occasionally need to generate URLs. In that case, you need to be able to find the base URL of the Django project within its Web server (normally, `reverse()` takes care of this for you). In that case, you can call `get_script_prefix()`, which will return the script prefix portion of the URL for your Django project. If your Django project is at the root of its web server, this is always `"/"`.