# documentación de Django - 1.10.7

# Código fuente para django.contrib.auth.context_processors

    # PermWrapper and PermLookupDict proxy the permissions system into objects that
    # the template system can understand.

    class PermLookupDict(object):
        def __init__(self, user, app_label):
            self.user, self.app_label = user, app_label

        def __repr__(self):
            return str(self.user.get_all_permissions())

        def __getitem__(self, perm_name):
            return self.user.has_perm("%s.%s" % (self.app_label, perm_name))

        def __iter__(self):
            # To fix 'item in perms.someapp' and __getitem__ interaction we need to
            # define __iter__. See #18979 for details.
            raise TypeError("PermLookupDict is not iterable.")

        def __bool__(self):
            return self.user.has_module_perms(self.app_label)

        def __nonzero__(self):      # Python 2 compatibility
            return type(self).__bool__(self)

    class PermWrapper(object):
        def __init__(self, user):
            self.user = user

        def __getitem__(self, app_label):
            return PermLookupDict(self.user, app_label)

        def __iter__(self):
            # I am large, I contain multitudes.
            raise TypeError("PermWrapper is not iterable.")

        def __contains__(self, perm_name):
            """
            Lookup by "someapp" or "someapp.someperm" in perms.
            """
            if '.' not in perm_name:
                # The name refers to module.
                return bool(self[perm_name])
            app_label, perm_name = perm_name.split('.', 1)
            return self[app_label][perm_name]

    def auth(request):
        """
        Returns context variables required by apps that use Django's authentication
        system.

        If there is no 'user' attribute in the request, uses AnonymousUser (from
        django.contrib.auth).
        """
        if hasattr(request, 'user'):
            user = request.user
        else:
            from django.contrib.auth.models import AnonymousUser
            user = AnonymousUser()

        return {
            'user': user,
            'perms': PermWrapper(user),
        }