Method _lookup_field

mongoengine/base/document.py:1064–1192

Given the path to a given field, return a list containing the Field object associated with that field and all of its parent Field objects. Args: parts (str, list, or tuple) - path to the field. Should be a string for simple fields existing on this doc

(cls, parts)

    @classmethod
    def _lookup_field(cls, parts):
        """Given the path to a given field, return a list containing
        the Field object associated with that field and all of its parent
        Field objects.

        Args:
            parts (str, list, or tuple) - path to the field. Should be a
            string for simple fields existing on this document or a list
            of strings for a field that exists deeper in embedded documents.

        Returns:
            A list of Field instances for fields that were found or
            strings for sub-fields that weren't.

        Example:
            >>> user._lookup_field('name')
            [<mongoengine.fields.StringField at 0x1119bff50>]

            >>> user._lookup_field('roles')
            [<mongoengine.fields.EmbeddedDocumentListField at 0x1119ec250>]

            >>> user._lookup_field(['roles', 'role'])
            [<mongoengine.fields.EmbeddedDocumentListField at 0x1119ec250>,
             <mongoengine.fields.StringField at 0x1119ec050>]

            >>> user._lookup_field('doesnt_exist')
            raises LookUpError

            >>> user._lookup_field(['roles', 'doesnt_exist'])
            [<mongoengine.fields.EmbeddedDocumentListField at 0x1119ec250>,
             'doesnt_exist']

        """
        # TODO this method is WAY too complicated. Simplify it.
        # TODO don't think returning a string for embedded non-existent fields is desired

        ListField = _import_class("ListField")
        DynamicField = _import_class("DynamicField")

        if not isinstance(parts, (list, tuple)):
            parts = [parts]

        fields = []
        field = None

        for field_name in parts:
            # Handle ListField indexing:
            if field_name.isdigit() and isinstance(field, ListField):
                fields.append(field_name)
                continue

            # Look up first field from the document
            if field is None:
                if field_name == "pk":
                    # Deal with "primary key" alias
                    field_name = cls._meta["id_field"]

                if field_name in cls._fields: