Use slots in common classes

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Changed
 
 - Write STAC v1.1.0 ([#1427](https://github.com/stac-utils/pystac/pull/1427))
+- Use `__slots__` for objects we expect to exist in large numbers ([#1434](https://github.com/stac-utils/pystac/pull/1434))
 
 ## [v1.11.0] - 2024-09-26
 

pystac/asset.py

@@ -37,6 +37,16 @@ class Asset:
             object JSON.
     """
 
+    __slots__: tuple[str, ...] = (
+        "href",
+        "title",
+        "description",
+        "media_type",
+        "roles",
+        "owner",
+        "extra_fields",
+    )
+
     href: str
     """Link to the asset object. Relative and absolute links are both allowed."""
 

pystac/catalog.py

@@ -133,6 +133,16 @@ class Catalog(STACObject):
             :class:`~pystac.layout.BestPracticesLayoutStrategy`.
     """
 
+    __slots__: tuple[str, ...] = STACObject.__slots__ + (
+        "catalog_type",
+        "description",
+        "extra_fields",
+        "title",
+        "_resolved_objects",
+        "_stac_io",
+        "strategy",
+    )
+
     catalog_type: CatalogType
     """The catalog type. Defaults to :attr:`CatalogType.ABSOLUTE_PUBLISHED`."""
 
@@ -159,7 +169,7 @@ class Catalog(STACObject):
 
     STAC_OBJECT_TYPE = pystac.STACObjectType.CATALOG
 
-    _stac_io: pystac.StacIO | None = None
+    _stac_io: pystac.StacIO | None
     """Optional instance of StacIO that will be used by default
     for any IO operations on objects contained by this catalog.
     Set while reading in a catalog. This is set when a catalog
@@ -207,6 +217,8 @@ def __init__(
 
         self._resolved_objects.cache(self)
 
+        self._stac_io = None
+
     def __repr__(self) -> str:
         return f"<Catalog id={self.id}>"
 

pystac/collection.py

@@ -479,6 +479,15 @@ class Collection(Catalog, Assets):
             :class:`~pystac.layout.BestPracticesLayoutStrategy`.
     """
 
+    __slots__: tuple[str, ...] = Catalog.__slots__ + (
+        "extent",
+        "license",
+        "keywords",
+        "providers",
+        "summaries",
+        "assets",
+    )
+
     description: str
     """Detailed multi-line description to fully explain the collection."""
 

pystac/item.py

@@ -67,6 +67,18 @@ class Item(STACObject, Assets):
             :attr:`~pystac.Asset.owner` attribute set to the created Item.
     """
 
+    __slots__: tuple[str, ...] = STACObject.__slots__ + (
+        "assets",
+        "bbox",
+        "collection",
+        "collection_id",
+        "datetime",
+        "extra_fields",
+        "geometry",
+        "links",
+        "properties",
+    )
+
     assets: dict[str, Asset]
     """Dictionary of :class:`~pystac.Asset` objects, each with a unique key."""
 
@@ -157,7 +169,8 @@ def __init__(
         if href is not None:
             self.set_self_href(href)
 
-        self.collection_id: str | None = None
+        self.collection_id = None
+        self.collection = None
         if collection is None:
             self.collection = None
         else:
@@ -175,30 +188,34 @@ def __repr__(self) -> str:
         return f"<Item id={self.id}>"
 
     def __getstate__(self) -> dict[str, Any]:
-        """Ensure that pystac does not encode too much information when pickling"""
-        d = self.__dict__.copy()
+        """Ensure that pystac does not encode too much information when pickling."""
+        state = {slot: getattr(self, slot) for slot in self.__slots__}
 
-        d["links"] = [
+        state["links"] = [
             (
                 link.to_dict(transform_href=False)
                 if link.get_href(transform_href=False)
                 else link
             )
-            for link in d["links"]
+            for link in state["links"]
         ]
 
-        return d
+        return state
 
     def __setstate__(self, state: dict[str, Any]) -> None:
         """Ensure that pystac knows how to decode the pickled object"""
-        d = state.copy()
-
-        d["links"] = [
-            Link.from_dict(link).set_owner(self) if isinstance(link, dict) else link
-            for link in d["links"]
-        ]
+        for slot in self.__slots__:
+            if slot == "links":
+                value = [
+                    Link.from_dict(link).set_owner(self)
+                    if isinstance(link, dict)
+                    else link
+                    for link in state["links"]
+                ]
+            else:
+                value = state.get(slot)  # type: ignore
 
-        self.__dict__ = d
+            setattr(self, slot, value)
 
     def set_self_href(self, href: str | None) -> None:
         """Sets the absolute HREF that is represented by the ``rel == 'self'``

pystac/link.py

@@ -70,6 +70,16 @@ class Link(PathLike):
             object JSON.
     """
 
+    __slots__: tuple[str, ...] = (
+        "rel",
+        "media_type",
+        "extra_fields",
+        "owner",
+        "_target_href",
+        "_target_object",
+        "_title",
+    )
+
     rel: str | pystac.RelType
     """The relation of the link (e.g. 'child', 'item'). Registered rel Types are
     preferred. See :class:`~pystac.RelType` for common media types."""

pystac/stac_object.py

@@ -41,6 +41,13 @@ class STACObject(ABC):
     functionality through the implementing classes.
     """
 
+    __slots__: tuple[str, ...] = (
+        "id",
+        "links",
+        "stac_extensions",
+        "_allow_parent_to_override_href",
+    )
+
     id: str
     """The ID of the STAC Object."""
 
@@ -53,12 +60,13 @@ class STACObject(ABC):
 
     STAC_OBJECT_TYPE: STACObjectType
 
-    _allow_parent_to_override_href: bool = True
+    _allow_parent_to_override_href: bool
     """Private attribute for whether parent objects should override on normalization"""
 
     def __init__(self, stac_extensions: list[str]) -> None:
         self.links = []
         self.stac_extensions = stac_extensions
+        self._allow_parent_to_override_href = True
 
     def validate(
         self,