Identifiers
Overview
Identifiers are components that tag resources with specific resource tags.
The following is an example of the MagicMimeIdentifier
, which uses libmagic file type identification to tag resources:
class MagicMimeIdentifier(Identifier[None]):
id = b"MagicMimeIdentifier"
targets = (File,)
_tags_by_mime: Dict[str, ResourceTag] = dict()
async def identify(self, resource: Resource, config=None):
_magic = await resource.analyze(Magic)
magic_mime = _magic.mime
tag = MagicMimeIdentifier._tags_by_mime.get(magic_mime)
if tag is not None:
resource.add_tag(tag)
@classmethod
def register(cls, resource: ResourceTag, mime_types: Union[Iterable[str], str]):
if isinstance(mime_types, str):
mime_types = [mime_types]
for mime_type in mime_types:
if mime_type in cls._tags_by_mime:
raise AlreadyExistError(f"Registering already-registered mime type: {mime_type}")
cls._tags_by_mime[mime_type] = resource
...
MagicMimeIdentifier.register(GenericText, "text/plain")
The last line of the example, MagicMimeIdentifier.register(GenericText, "text/plain")
, registers the "text/plain" pattern as one that maps to the GenericText
resource tag.
Usage
Identifiers can be explicitly run using the Resource.identify
method:
await resource.identify()
Note that running identifiers explicitly is often not needed, as Resource.unpack
runs all registered identifiers before running
unpackers.
![](../../assets/square_05.png)