Source code for django.urls.resolvers

This module converts requested URLs to callback view functions.

URLResolver is the main class here. Its resolve() method takes a URL (as
a string) and returns a ResolverMatch object which provides access to all
attributes of the resolved URL match.
import functools
import inspect
import re
import threading
from importlib import import_module
from urllib.parse import quote

from django.conf import settings
from django.core.checks import Error, Warning
from django.core.checks.urls import check_resolver
from django.core.exceptions import ImproperlyConfigured, ViewDoesNotExist
from django.utils.datastructures import MultiValueDict
from django.utils.functional import cached_property
from django.utils.http import RFC3986_SUBDELIMS, escape_leading_slashes
from django.utils.regex_helper import normalize
from django.utils.translation import get_language

from .converters import get_converter
from .exceptions import NoReverseMatch, Resolver404
from .utils import get_callable

[docs]class ResolverMatch:
    def __init__(self, func, args, kwargs, url_name=None, app_names=None, namespaces=None, route=None):
        self.func = func
        self.args = args
        self.kwargs = kwargs
        self.url_name = url_name
        self.route = route

        # If a URLRegexResolver doesn't have a namespace or app_name, it passes
        # in an empty value.
        self.app_names = [x for x in app_names if x] if app_names else []
        self.app_name = ':'.join(self.app_names)
        self.namespaces = [x for x in namespaces if x] if namespaces else []
        self.namespace = ':'.join(self.namespaces)

        if not hasattr(func, '__name__'):
            # A class-based view
            self._func_path = func.__class__.__module__ + '.' + func.__class__.__name__
            # A function-based view
            self._func_path = func.__module__ + '.' + func.__name__

        view_path = url_name or self._func_path
        self.view_name = ':'.join(self.namespaces + [view_path])

    def __getitem__(self, index):
        return (self.func, self.args, self.kwargs)[index]

    def __repr__(self):
        return "ResolverMatch(func=%s, args=%s, kwargs=%s, url_name=%s, app_names=%s, namespaces=%s, route=%s)" % (
            self._func_path, self.args, self.kwargs, self.url_name,
            self.app_names, self.namespaces, self.route,

def get_resolver(urlconf=None):
    if urlconf is None:
        urlconf = settings.ROOT_URLCONF
    return URLResolver(RegexPattern(r'^/'), urlconf)

def get_ns_resolver(ns_pattern, resolver, converters):
    # Build a namespaced resolver for the given parent URLconf pattern.
    # This makes it possible to have captured parameters in the parent
    # URLconf pattern.
    pattern = RegexPattern(ns_pattern)
    pattern.converters = dict(converters)
    ns_resolver = URLResolver(pattern, resolver.url_patterns)
    return URLResolver(RegexPattern(r'^/'), [ns_resolver])

class LocaleRegexDescriptor:
    def __init__(self, attr):
        self.attr = attr

    def __get__(self, instance, cls=None):
        Return a compiled regular expression based on the active language.
        if instance is None:
            return self
        # As a performance optimization, if the given regex string is a regular
        # string (not a lazily-translated string proxy), compile it once and
        # avoid per-language compilation.
        pattern = getattr(instance, self.attr)
        if isinstance(pattern, str):
            instance.__dict__['regex'] = instance._compile(pattern)
            return instance.__dict__['regex']
        language_code = get_language()
        if language_code not in instance._regex_dict:
            instance._regex_dict[language_code] = instance._compile(str(pattern))
        return instance._regex_dict[language_code]

class CheckURLMixin:
    def describe(self):
        Format the URL pattern for display in warning messages.
        description = "'{}'".format(self)
            description += " [name='{}']".format(
        return description

    def _check_pattern_startswith_slash(self):
        Check that the pattern does not begin with a forward slash.
        regex_pattern = self.regex.pattern
        if not settings.APPEND_SLASH:
            # Skip check as it can be useful to start a URL pattern with a slash
            # when APPEND_SLASH=False.
            return []
        if regex_pattern.startswith(('/', '^/', '^\\/')) and not regex_pattern.endswith('/'):
            warning = Warning(
                "Your URL pattern {} has a route beginning with a '/'. Remove this "
                "slash as it is unnecessary. If this pattern is targeted in an "
                "include(), ensure the include() pattern has a trailing '/'.".format(
            return [warning]
            return []

class RegexPattern(CheckURLMixin):
    regex = LocaleRegexDescriptor('_regex')

    def __init__(self, regex, name=None, is_endpoint=False):
        self._regex = regex
        self._regex_dict = {}
        self._is_endpoint = is_endpoint = name
        self.converters = {}

    def match(self, path):
        match =
        if match:
            # If there are any named groups, use those as kwargs, ignoring
            # non-named groups. Otherwise, pass all non-named arguments as
            # positional arguments.
            kwargs = match.groupdict()
            args = () if kwargs else match.groups()
            return path[match.end():], args, kwargs
        return None

    def check(self):
        warnings = []
        if not self._is_endpoint:
        return warnings

    def _check_include_trailing_dollar(self):
        regex_pattern = self.regex.pattern
        if regex_pattern.endswith('$') and not regex_pattern.endswith(r'\$'):
            return [Warning(
                "Your URL pattern {} uses include with a route ending with a '$'. "
                "Remove the dollar from the route to avoid problems including "
            return []

    def _compile(self, regex):
        """Compile and return the given regular expression."""
            return re.compile(regex)
        except re.error as e:
            raise ImproperlyConfigured(
                '"%s" is not a valid regular expression: %s' % (regex, e)

    def __str__(self):
        return str(self._regex)


def _route_to_regex(route, is_endpoint=False):
    Convert a path pattern into a regular expression. Return the regular
    expression and a dictionary mapping the capture names to the converters.
    For example, 'foo/' returns '^foo\\/(?P[0-9]+)'
    and {'pk': }.
    original_route = route
    parts = ['^']
    converters = {}
    while True:
        match =
        if not match:
        route = route[match.end():]
        parameter ='parameter')
        if not parameter.isidentifier():
            raise ImproperlyConfigured(
                "URL route '%s' uses parameter name %r which isn't a valid "
                "Python identifier." % (original_route, parameter)
        raw_converter ='converter')
        if raw_converter is None:
            # If a converter isn't specified, the default is `str`.
            raw_converter = 'str'
            converter = get_converter(raw_converter)
        except KeyError as e:
            raise ImproperlyConfigured(
                "URL route '%s' uses invalid converter %s." % (original_route, e)
        converters[parameter] = converter
        parts.append('(?P + parameter + '>' + converter.regex + ')')
    if is_endpoint:
    return ''.join(parts), converters

class RoutePattern(CheckURLMixin):
    regex = LocaleRegexDescriptor('_route')

    def __init__(self, route, name=None, is_endpoint=False):
        self._route = route
        self._regex_dict = {}
        self._is_endpoint = is_endpoint = name
        self.converters = _route_to_regex(str(route), is_endpoint)[1]

    def match(self, path):
        match =
        if match:
            # RoutePattern doesn't allow non-named groups so args are ignored.
            kwargs = match.groupdict()
            for key, value in kwargs.items():
                converter = self.converters[key]
                    kwargs[key] = converter.to_python(value)
                except ValueError:
                    return None
            return path[match.end():], (), kwargs
        return None

    def check(self):
        warnings = self._check_pattern_startswith_slash()
        route = self._route
        if '(?P in route or route.startswith('^') or route.endswith('$'):
                "Your URL pattern {} has a route that contains '(?P
                "with a '^', or ends with a '$'. This was likely an oversight "
                "when migrating to django.urls.path().".format(self.describe()),
        return warnings

    def _compile(self, route):
        return re.compile(_route_to_regex(route, self._is_endpoint)[0])

    def __str__(self):
        return str(self._route)

class LocalePrefixPattern:
    def __init__(self, prefix_default_language=True):
        self.prefix_default_language = prefix_default_language
        self.converters = {}

    def regex(self):
        # This is only used by reverse() and cached in _reverse_dict.
        return re.compile(self.language_prefix)

    def language_prefix(self):
        language_code = get_language() or settings.LANGUAGE_CODE
        if language_code == settings.LANGUAGE_CODE and not self.prefix_default_language:
            return ''
            return '%s/' % language_code

    def match(self, path):
        language_prefix = self.language_prefix
        if path.startswith(language_prefix):
            return path[len(language_prefix):], (), {}
        return None

    def check(self):
        return []

    def describe(self):
        return "'{}'".format(self)

    def __str__(self):
        return self.language_prefix

class URLPattern:
    def __init__(self, pattern, callback, default_args=None, name=None):
        self.pattern = pattern
        self.callback = callback  # the view
        self.default_args = default_args or {} = name

    def __repr__(self):
        return '<%s %s>' % (self.__class__.__name__, self.pattern.describe())

    def check(self):
        warnings = self._check_pattern_name()
        return warnings

    def _check_pattern_name(self):
        Check that the pattern name does not contain a colon.
        if is not None and ":" in
            warning = Warning(
                "Your URL pattern {} has a name including a ':'. Remove the colon, to "
                "avoid ambiguous namespace references.".format(self.pattern.describe()),
            return [warning]
            return []

    def resolve(self, path):
        match = self.pattern.match(path)
        if match:
            new_path, args, kwargs = match
            # Pass any extra_kwargs as **kwargs.
            return ResolverMatch(self.callback, args, kwargs,, route=str(self.pattern))

    def lookup_str(self):
        A string that identifies the view (e.g. '' or
        callback = self.callback
        if isinstance(callback, functools.partial):
            callback = callback.func
        if not hasattr(callback, '__name__'):
            return callback.__module__ + "." + callback.__class__.__name__
        return callback.__module__ + "." + callback.__qualname__

class URLResolver:
    def __init__(self, pattern, urlconf_name, default_kwargs=None, app_name=None, namespace=None):
        self.pattern = pattern
        # urlconf_name is the dotted Python path to the module defining
        # urlpatterns. It may also be an object with an urlpatterns attribute
        # or urlpatterns itself.
        self.urlconf_name = urlconf_name
        self.callback = None
        self.default_kwargs = default_kwargs or {}
        self.namespace = namespace
        self.app_name = app_name
        self._reverse_dict = {}
        self._namespace_dict = {}
        self._app_dict = {}
        # set of dotted paths to all functions and classes that are used in
        # urlpatterns
        self._callback_strs = set()
        self._populated = False
        self._local = threading.local()
        self._urlconf_lock = threading.Lock()

    def __repr__(self):
        if isinstance(self.urlconf_name, list) and self.urlconf_name:
            # Don't bother to output the whole list, it can be huge
            urlconf_repr = '<%s list>' % self.urlconf_name[0].__class__.__name__
            urlconf_repr = repr(self.urlconf_name)
        return '<%s %s (%s:%s) %s>' % (
            self.__class__.__name__, urlconf_repr, self.app_name,
            self.namespace, self.pattern.describe(),

    def check(self):
        messages = []
        for pattern in self.url_patterns:
        return messages or self.pattern.check()

    def _check_custom_error_handlers(self):
        messages = []
        # All handlers take (request, exception) arguments except handler500
        # which takes (request).
        for status_code, num_parameters in [(400, 2), (403, 2), (404, 2), (500, 1)]:
                handler, param_dict = self.resolve_error_handler(status_code)
            except (ImportError, ViewDoesNotExist) as e:
                path = getattr(self.urlconf_module, 'handler%s' % status_code)
                msg = (
                    "The custom handler{status_code} view '{path}' could not be imported."
                ).format(status_code=status_code, path=path)
                messages.append(Error(msg, hint=str(e), id='urls.E008'))
            signature = inspect.signature(handler)
            args = [None] * num_parameters
            except TypeError:
                msg = (
                    "The custom handler{status_code} view '{path}' does not "
                    "take the correct number of arguments ({args})."
                    path=handler.__module__ + '.' + handler.__qualname__,
                    args='request, exception' if num_parameters == 2 else 'request',
                messages.append(Error(msg, id='urls.E007'))
        return messages

    def _populate(self):
        # Short-circuit if called recursively in this thread to prevent
        # infinite recursion. Concurrent threads may call this at the same
        # time and will need to continue, so set 'populating' on a
        # thread-local variable.
        if getattr(self._local, 'populating', False):
            self._local.populating = True
            lookups = MultiValueDict()
            namespaces = {}
            apps = {}
            language_code = get_language()
            for url_pattern in reversed(self.url_patterns):
                p_pattern = url_pattern.pattern.regex.pattern
                if p_pattern.startswith('^'):
                    p_pattern = p_pattern[1:]
                if isinstance(url_pattern, URLPattern):
                    bits = normalize(url_pattern.pattern.regex.pattern)
                        (bits, p_pattern, url_pattern.default_args, url_pattern.pattern.converters)
                    if is not None:
                            (bits, p_pattern, url_pattern.default_args, url_pattern.pattern.converters)
                else:  # url_pattern is a URLResolver.
                    if url_pattern.app_name:
                        apps.setdefault(url_pattern.app_name, []).append(url_pattern.namespace)
                        namespaces[url_pattern.namespace] = (p_pattern, url_pattern)
                        for name in url_pattern.reverse_dict:
                            for matches, pat, defaults, converters in url_pattern.reverse_dict.getlist(name):
                                new_matches = normalize(p_pattern + pat)
                                        p_pattern + pat,
                                        {**defaults, **url_pattern.default_kwargs},
                                        {**self.pattern.converters, **url_pattern.pattern.converters, **converters}
                        for namespace, (prefix, sub_pattern) in url_pattern.namespace_dict.items():
                            current_converters = url_pattern.pattern.converters
                            namespaces[namespace] = (p_pattern + prefix, sub_pattern)
                        for app_name, namespace_list in url_pattern.app_dict.items():
                            apps.setdefault(app_name, []).extend(namespace_list)
            self._namespace_dict[language_code] = namespaces
            self._app_dict[language_code] = apps
            self._reverse_dict[language_code] = lookups
            self._populated = True
            self._local.populating = False

    def reverse_dict(self):
        language_code = get_language()
        if language_code not in self._reverse_dict:
        return self._reverse_dict[language_code]

    def namespace_dict(self):
        language_code = get_language()
        if language_code not in self._namespace_dict:
        return self._namespace_dict[language_code]

    def app_dict(self):
        language_code = get_language()
        if language_code not in self._app_dict:
        return self._app_dict[language_code]

    def _join_route(route1, route2):
        """Join two routes, without the starting ^ in the second route."""
        if not route1:
            return route2
        if route2.startswith('^'):
            route2 = route2[1:]
        return route1 + route2

    def _is_callback(self, name):
        if not self._populated:
        return name in self._callback_strs

    def resolve(self, path):
        path = str(path)  # path may be a reverse_lazy object
        tried = []
        match = self.pattern.match(path)
        if match:
            new_path, args, kwargs = match
            for pattern in self.url_patterns:
                    sub_match = pattern.resolve(new_path)
                except Resolver404 as e:
                    sub_tried = e.args[0].get('tried')
                    if sub_tried is not None:
                        tried.extend([pattern] + t for t in sub_tried)
                    if sub_match:
                        # Merge captured arguments in match with submatch
                        sub_match_dict = {**kwargs, **self.default_kwargs}
                        # Update the sub_match_dict with the kwargs from the sub_match.
                        # If there are *any* named groups, ignore all non-named groups.
                        # Otherwise, pass all non-named arguments as positional arguments.
                        sub_match_args = sub_match.args
                        if not sub_match_dict:
                            sub_match_args = args + sub_match.args
                        current_route = '' if isinstance(pattern, URLPattern) else str(pattern.pattern)
                        return ResolverMatch(
                            [self.app_name] + sub_match.app_names,
                            [self.namespace] + sub_match.namespaces,
                            self._join_route(current_route, sub_match.route),
            raise Resolver404({'tried': tried, 'path': new_path})
        raise Resolver404({'path': path})

    def urlconf_module(self):
        # import_module is not thread safe if the module throws an exception
        # during import, and can return an empty module object in Python < 3.6
        # (see
        with self._urlconf_lock:
            if isinstance(self.urlconf_name, str):
                return import_module(self.urlconf_name)
                return self.urlconf_name

    def url_patterns(self):
        # urlconf_module might be a valid set of patterns, so we default to it
        patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
        except TypeError:
            msg = (
                "The included URLconf '{name}' 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."
            raise ImproperlyConfigured(msg.format(name=self.urlconf_name))
        return patterns

    def resolve_error_handler(self, view_type):
        callback = getattr(self.urlconf_module, 'handler%s' % view_type, None)
        if not callback:
            # No handler specified in file; use lazy import, since
            # django.conf.urls imports this file.
            from django.conf import urls
            callback = getattr(urls, 'handler%s' % view_type)
        return get_callable(callback), {}

    def reverse(self, lookup_view, *args, **kwargs):
        return self._reverse_with_prefix(lookup_view, '', *args, **kwargs)

    def _reverse_with_prefix(self, lookup_view, _prefix, *args, **kwargs):
        if args and kwargs:
            raise ValueError("Don't mix *args and **kwargs in call to reverse()!")

        if not self._populated:

        possibilities = self.reverse_dict.getlist(lookup_view)

        for possibility, pattern, defaults, converters in possibilities:
            for result, params in possibility:
                if args:
                    if len(args) != len(params):
                    candidate_subs = dict(zip(params, args))
                    if set(kwargs).symmetric_difference(params).difference(defaults):
                    if any(kwargs.get(k, v) != v for k, v in defaults.items()):
                    candidate_subs = kwargs
                # Convert the candidate subs to text using Converter.to_url().
                text_candidate_subs = {}
                for k, v in candidate_subs.items():
                    if k in converters:
                        text_candidate_subs[k] = converters[k].to_url(v)
                        text_candidate_subs[k] = str(v)
                # WSGI provides decoded URLs, without %xx escapes, and the URL
                # resolver operates on such URLs. First substitute arguments
                # without quoting to build a decoded URL and look for a match.
                # Then, if we have a match, redo the substitution with quoted
                # arguments in order to return a properly encoded URL.
                candidate_pat = _prefix.replace('%', '%%') + result
                if'^%s%s' % (re.escape(_prefix), pattern), candidate_pat % text_candidate_subs):
                    # safe characters from `pchar` definition of RFC 3986
                    url = quote(candidate_pat % text_candidate_subs, safe=RFC3986_SUBDELIMS + '/~:@')
                    # Don't allow construction of scheme relative urls.
                    return escape_leading_slashes(url)
        # lookup_view can be URL name or callable, but callables are not
        # friendly in error messages.
        m = getattr(lookup_view, '__module__', None)
        n = getattr(lookup_view, '__name__', None)
        if m is not None and n is not None:
            lookup_view_s = "%s.%s" % (m, n)
            lookup_view_s = lookup_view

        patterns = [pattern for (_, pattern, _, _) in possibilities]
        if patterns:
            if args:
                arg_msg = "arguments '%s'" % (args,)
            elif kwargs:
                arg_msg = "keyword arguments '%s'" % (kwargs,)
                arg_msg = "no arguments"
            msg = (
                "Reverse for '%s' with %s not found. %d pattern(s) tried: %s" %
                (lookup_view_s, arg_msg, len(patterns), patterns)
            msg = (
                "Reverse for '%(view)s' not found. '%(view)s' is not "
                "a valid view function or pattern name." % {'view': lookup_view_s}
        raise NoReverseMatch(msg)