# Django 2.2.9.dev20191202104323 文档

# django.core.exceptions 源代码

    """
    Global Django exception and warning classes.
    """

    class FieldDoesNotExist(Exception):
        """The requested model field does not exist"""
        pass

    class AppRegistryNotReady(Exception):
        """The django.apps registry is not populated yet"""
        pass

    class ObjectDoesNotExist(Exception):
        """The requested object does not exist"""
        silent_variable_failure = True

    class MultipleObjectsReturned(Exception):
        """The query returned multiple objects when only one was expected."""
        pass

    class SuspiciousOperation(Exception):
        """The user did something suspicious"""

    class SuspiciousMultipartForm(SuspiciousOperation):
        """Suspect MIME request in multipart form data"""
        pass

    class SuspiciousFileOperation(SuspiciousOperation):
        """A Suspicious filesystem operation was attempted"""
        pass

    class DisallowedHost(SuspiciousOperation):
        """HTTP_HOST header contains invalid value"""
        pass

    class DisallowedRedirect(SuspiciousOperation):
        """Redirect to scheme not in allowed list"""
        pass

    class TooManyFieldsSent(SuspiciousOperation):
        """
        The number of fields in a GET or POST request exceeded
        settings.DATA_UPLOAD_MAX_NUMBER_FIELDS.
        """
        pass

    class RequestDataTooBig(SuspiciousOperation):
        """
        The size of the request (excluding any file uploads) exceeded
        settings.DATA_UPLOAD_MAX_MEMORY_SIZE.
        """
        pass

    class PermissionDenied(Exception):
        """The user did not have permission to do that"""
        pass

    class ViewDoesNotExist(Exception):
        """The requested view does not exist"""
        pass

    class MiddlewareNotUsed(Exception):
        """This middleware is not used in this server configuration"""
        pass

    class ImproperlyConfigured(Exception):
        """Django is somehow improperly configured"""
        pass

    class FieldError(Exception):
        """Some kind of problem with a model field."""
        pass

    NON_FIELD_ERRORS = '__all__'

    class ValidationError(Exception):
        """An error while validating data."""
        def __init__(self, message, code=None, params=None):
            """
            The `message` argument can be a single error, a list of errors, or a
            dictionary that maps field names to lists of errors. What we define as
            an "error" can be either a simple string or an instance of
            ValidationError with its message attribute set, and what we define as
            list or dictionary can be an actual `list` or `dict` or an instance
            of ValidationError with its `error_list` or `error_dict` attribute set.
            """
            super().__init__(message, code, params)

            if isinstance(message, ValidationError):
                if hasattr(message, 'error_dict'):
                    message = message.error_dict
                elif not hasattr(message, 'message'):
                    message = message.error_list
                else:
                    message, code, params = message.message, message.code, message.params

            if isinstance(message, dict):
                self.error_dict = {}
                for field, messages in message.items():
                    if not isinstance(messages, ValidationError):
                        messages = ValidationError(messages)
                    self.error_dict[field] = messages.error_list

            elif isinstance(message, list):
                self.error_list = []
                for message in message:
                    # Normalize plain strings to instances of ValidationError.
                    if not isinstance(message, ValidationError):
                        message = ValidationError(message)
                    if hasattr(message, 'error_dict'):
                        self.error_list.extend(sum(message.error_dict.values(), []))
                    else:
                        self.error_list.extend(message.error_list)

            else:
                self.message = message
                self.code = code
                self.params = params
                self.error_list = [self]

        @property
        def message_dict(self):
            # Trigger an AttributeError if this ValidationError
            # doesn't have an error_dict.
            getattr(self, 'error_dict')

            return dict(self)

        @property
        def messages(self):
            if hasattr(self, 'error_dict'):
                return sum(dict(self).values(), [])
            return list(self)

        def update_error_dict(self, error_dict):
            if hasattr(self, 'error_dict'):
                for field, error_list in self.error_dict.items():
                    error_dict.setdefault(field, []).extend(error_list)
            else:
                error_dict.setdefault(NON_FIELD_ERRORS, []).extend(self.error_list)
            return error_dict

        def __iter__(self):
            if hasattr(self, 'error_dict'):
                for field, errors in self.error_dict.items():
                    yield field, list(ValidationError(errors))
            else:
                for error in self.error_list:
                    message = error.message
                    if error.params:
                        message %= error.params
                    yield str(message)

        def __str__(self):
            if hasattr(self, 'error_dict'):
                return repr(dict(self))
            return repr(list(self))

        def __repr__(self):
            return 'ValidationError(%s)' % self

    class EmptyResultSet(Exception):
        """A database query predicate is impossible."""
        pass