Speed up importing pystac

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [Unreleased]
 
+- Speed up importing pystac ([#1584](https://github.com/stac-utils/pystac/pull/1584))
+
 ## [v1.14.1] - 2025-09-18
 
 ### Fixed

pystac/__init__.py

@@ -44,7 +44,6 @@
     "set_stac_version",
 ]
 
-import os
 import warnings
 from typing import Any
 
@@ -199,6 +198,8 @@ def write_file(
     """
     if stac_io is None:
         stac_io = StacIO.default()
+    import os
+
     dest_href = None if dest_href is None else str(os.fspath(dest_href))
     obj.save_object(
         include_self_link=include_self_link, dest_href=dest_href, stac_io=stac_io

pystac/asset.py

@@ -1,13 +1,10 @@
 from __future__ import annotations
 
-import os
 import shutil
 from copy import copy, deepcopy
-from html import escape
 from typing import TYPE_CHECKING, Any, Protocol, TypeVar
 
 from pystac import MediaType, STACError, common_metadata, utils
-from pystac.html.jinja_env import get_jinja_env
 from pystac.utils import is_absolute_href, make_absolute_href, make_relative_href
 
 if TYPE_CHECKING:
@@ -182,6 +179,10 @@ def __repr__(self) -> str:
         return f"<Asset href={self.href}>"
 
     def _repr_html_(self) -> str:
+        from html import escape
+
+        from pystac.html.jinja_env import get_jinja_env
+
         jinja_env = get_jinja_env()
         if jinja_env:
             template = jinja_env.get_template("JSON.jinja2")
@@ -259,6 +260,8 @@ def delete(self) -> None:
 
         Does not modify the asset.
         """
+        import os
+
         href = _absolute_href(self.href, self.owner, "delete")
         os.remove(href)
 

pystac/catalog.py

@@ -1,10 +1,8 @@
 from __future__ import annotations
 
 import os
-import warnings
 from collections.abc import Callable, Iterable, Iterator
 from copy import deepcopy
-from itertools import chain
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -521,6 +519,8 @@ def get_item(self, id: str, recursive: bool = False) -> Item | None:
         Return:
             Item or None: The item with the given ID, or None if not found.
         """
+        import warnings
+
         warnings.warn(
             "get_item is deprecated and will be removed in v2. "
             "Use next(self.get_items(id), None) instead",
@@ -549,6 +549,8 @@ def get_items(self, *ids: str, recursive: bool = False) -> Iterator[Item]:
                 (if recursive) all catalogs or collections connected to this catalog
                 through child links.
         """
+        from itertools import chain
+
         items: Iterator[Item]
         if not recursive:
             items = map(
@@ -615,6 +617,9 @@ def get_all_items(self) -> Iterator[Item]:
                 catalogs or collections connected to this catalog through
                 child links.
         """
+        import warnings
+        from itertools import chain
+
         warnings.warn(
             "get_all_items is deprecated and will be removed in v2",
             DeprecationWarning,

pystac/collection.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import warnings
 from collections.abc import Iterable, Sequence
 from copy import deepcopy
 from datetime import datetime, timezone
@@ -12,8 +11,6 @@
     cast,
 )
 
-from dateutil import tz
-
 import pystac
 from pystac import CatalogType, STACObjectType
 from pystac.asset import Asset, Assets
@@ -257,6 +254,8 @@ def from_dict(d: dict[str, Any]) -> TemporalExtent:
         parsed_intervals: list[list[datetime | None]] = []
         for i in d["interval"]:
             if isinstance(i, str):
+                import warnings
+
                 # d["interval"] is a list of strings, so we correct the list and
                 # try again
                 # https://github.com/stac-utils/pystac/issues/1221
@@ -384,6 +383,8 @@ def from_items(
             Extent: An Extent that spatially and temporally covers all of the
             given items.
         """
+        from dateutil import tz
+
         bounds_values: list[list[float]] = [
             [float("inf")],
             [float("inf")],
@@ -635,6 +636,8 @@ def from_dict(
         migrate: bool = True,
         preserve_dict: bool = True,
     ) -> C:
+        import warnings
+
         from pystac.extensions.version import CollectionVersionExtension
 
         if migrate:

pystac/extensions/eo.py

@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import warnings
 from collections.abc import Iterable
 from typing import (
     Any,
@@ -386,6 +385,8 @@ def get_schema_uri(cls) -> str:
 
     @classmethod
     def get_schema_uris(cls) -> list[str]:
+        import warnings
+
         warnings.warn(
             "get_schema_uris is deprecated and will be removed in v2",
             DeprecationWarning,

pystac/extensions/file.py

@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import warnings
 from collections.abc import Iterable
 from typing import Any, Generic, Literal, TypeVar, cast
 
@@ -370,6 +369,8 @@ def migrate(
                 found_fields[asset_key] = values
 
         if found_fields:
+            import warnings
+
             warnings.warn(
                 f"Assets {list(found_fields.keys())} contain fields: "
                 f"{list(set.union(*found_fields.values()))} which "

pystac/extensions/grid.py

@@ -3,7 +3,6 @@
 from __future__ import annotations
 
 import re
-import warnings
 from re import Pattern
 from typing import Any, Literal
 
@@ -92,6 +91,8 @@ def get_schema_uri(cls) -> str:
 
     @classmethod
     def get_schema_uris(cls) -> list[str]:
+        import warnings
+
         warnings.warn(
             "get_schema_uris is deprecated and will be removed in v2",
             DeprecationWarning,

pystac/extensions/item_assets.py

@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import warnings
 from typing import Any, Literal
 
 import pystac
@@ -27,6 +26,8 @@ class AssetDefinition(ItemAssetDefinition):
     """
 
     def __init__(cls, *args: Any, **kwargs: Any) -> None:
+        import warnings
+
         warnings.warn(
             (
                 "``AssetDefinition`` is deprecated. "
@@ -49,6 +50,8 @@ class ItemAssetsExtension(ExtensionManagementMixin[pystac.Collection]):
     collection: pystac.Collection
 
     def __init__(self, collection: pystac.Collection) -> None:
+        import warnings
+
         warnings.warn(
             (
                 "The ``item_assets`` extension is deprecated. "

pystac/extensions/projection.py

@@ -2,8 +2,6 @@
 
 from __future__ import annotations
 
-import json
-import warnings
 from collections.abc import Iterable
 from typing import (
     Any,
@@ -223,6 +221,8 @@ def crs_string(self) -> str | None:
         elif self.wkt2:
             return self.wkt2
         elif self.projjson:
+            import json
+
             return json.dumps(self.projjson)
         else:
             return None
@@ -321,6 +321,8 @@ def get_schema_uri(cls) -> str:
 
     @classmethod
     def get_schema_uris(cls) -> list[str]:
+        import warnings
+
         warnings.warn(
             "get_schema_uris is deprecated and will be removed in v2",
             DeprecationWarning,

pystac/extensions/raster.py

@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import warnings
 from collections.abc import Iterable
 from typing import (
     Any,
@@ -716,6 +715,8 @@ def get_schema_uri(cls) -> str:
 
     @classmethod
     def get_schema_uris(cls) -> list[str]:
+        import warnings
+
         warnings.warn(
             "get_schema_uris is deprecated and will be removed in v2",
             DeprecationWarning,

pystac/extensions/scientific.py

@@ -7,9 +7,7 @@
 
 from __future__ import annotations
 
-import copy
 from typing import Any, Generic, Literal, TypeVar, cast
-from urllib import parse
 
 import pystac
 from pystac.extensions.base import (
@@ -49,6 +47,8 @@ class ScientificRelType(StringEnum):
 
 def doi_to_url(doi: str) -> str:
     """Converts a DOI to the corresponding URL."""
+    from urllib import parse
+
     return DOI_URL_BASE + parse.quote(doi)
 
 
@@ -72,6 +72,8 @@ def __repr__(self) -> str:
         return f"<Publication doi={self.doi} target={self.citation}>"
 
     def to_dict(self) -> dict[str, str | None]:
+        import copy
+
         return copy.deepcopy({"doi": self.doi, "citation": self.citation})
 
     @staticmethod

pystac/extensions/version.py

@@ -2,7 +2,6 @@
 
 from __future__ import annotations
 
-import warnings
 from collections.abc import Generator
 from contextlib import contextmanager
 from typing import (
@@ -437,6 +436,8 @@ def ignore_deprecated() -> Generator[None]:
     """Context manager for suppressing the :class:`pystac.DeprecatedWarning`
     when creating a deprecated :class:`~pystac.Item` or :class:`~pystac.Collection`
     from a dictionary."""
+    import warnings
+
     with warnings.catch_warnings():
         warnings.simplefilter("ignore", category=DeprecatedWarning)
         yield

pystac/item.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-import warnings
 from copy import copy, deepcopy
 from typing import TYPE_CHECKING, Any, TypeVar, cast
 
@@ -419,6 +418,8 @@ def from_dict(
         migrate: bool = True,
         preserve_dict: bool = True,
     ) -> T:
+        import warnings
+
         from pystac.extensions.version import ItemVersionExtension
 
         if preserve_dict:

pystac/item_assets.py

@@ -6,7 +6,6 @@
 
 from __future__ import annotations
 
-from copy import deepcopy
 from typing import TYPE_CHECKING, Any
 
 import pystac
@@ -179,6 +178,8 @@ def roles(self, v: list[str] | None) -> None:
 
     def to_dict(self) -> dict[str, Any]:
         """Returns a dictionary representing this ``ItemAssetDefinition``."""
+        from copy import deepcopy
+
         return deepcopy(self.properties)
 
     def create_asset(self, href: str) -> pystac.Asset:

pystac/item_collection.py

@@ -1,8 +1,6 @@
 from __future__ import annotations
 
 from collections.abc import Collection, Iterable, Iterator
-from copy import deepcopy
-from html import escape
 from typing import (
     Any,
     TypeAlias,
@@ -11,7 +9,6 @@
 
 import pystac
 from pystac.errors import STACTypeError
-from pystac.html.jinja_env import get_jinja_env
 from pystac.serialization.identify import identify_stac_object_type
 from pystac.utils import HREF, is_absolute_href, make_absolute_href, make_posix_style
 
@@ -147,6 +144,10 @@ def to_dict(self, transform_hrefs: bool = False) -> dict[str, Any]:
         }
 
     def _repr_html_(self) -> str:
+        from html import escape
+
+        from pystac.html.jinja_env import get_jinja_env
+
         jinja_env = get_jinja_env()
         if jinja_env:
             template = jinja_env.get_template("JSON.jinja2")
@@ -158,6 +159,8 @@ def clone(self) -> ItemCollection:
         """Creates a clone of this instance. This clone is a deep copy; all
         :class:`~pystac.Item` instances are cloned and all additional top-level fields
         are deep copied."""
+        from copy import deepcopy
+
         return self.__class__(
             items=[item.clone() for item in self.items],
             extra_fields=deepcopy(self.extra_fields),