Instantiate default client lazily (#432)

* lazy default client

* Add note to changelog

* pr number in history

* Validate in cloudpath

HISTORY.md

@@ -6,6 +6,7 @@
 - Fix `CloudPath` cleanup via `CloudPath.__del__` when `Client` encounters an exception during initialization and does not create a `file_cache_mode` attribute. (Issue [#372](https://github.com/drivendataorg/cloudpathlib/issues/372), thanks to [@bryanwweber](https://github.com/bryanwweber)) 
 - Drop support for Python 3.7; pin minimal `boto3` version to Python 3.8+ versions. (PR [#407](https://github.com/drivendataorg/cloudpathlib/pull/407))
 - fix: use native `exists()` method in `GSClient`. (PR [#420](https://github.com/drivendataorg/cloudpathlib/pull/420))
+- Enhancement: lazy instantiation of default client (PR [#432](https://github.com/drivendataorg/cloudpathlib/issues/432), Issue [#428](https://github.com/drivendataorg/cloudpathlib/issues/428))
 
 ## v0.18.1 (2024-02-26)
 

cloudpathlib/cloudpath.py

@@ -214,8 +214,10 @@ def __init__(
         # handle if local file gets opened. must be set at the top of the method in case any code
         # below raises an exception, this prevents __del__ from raising an AttributeError
         self._handle: Optional[IO] = None
+        self._client: Optional["Client"] = None
 
         self.is_valid_cloudpath(cloud_path, raise_on_error=True)
+        self._cloud_meta.validate_completeness()
 
         # versions of the raw string that provide useful methods
         self._str = str(cloud_path)
@@ -225,41 +227,46 @@ def __init__(
         # setup client
         if client is None:
             if isinstance(cloud_path, CloudPath):
-                client = cloud_path.client
-            else:
-                client = self._cloud_meta.client_class.get_default_client()
-        if not isinstance(client, self._cloud_meta.client_class):
+                self._client = cloud_path.client
+        else:
+            self._client = client
+
+        if client is not None and not isinstance(client, self._cloud_meta.client_class):
             raise ClientMismatchError(
                 f"Client of type [{client.__class__}] is not valid for cloud path of type "
                 f"[{self.__class__}]; must be instance of [{self._cloud_meta.client_class}], or "
                 f"None to use default client for this cloud path class."
             )
-        self.client: Client = client
 
         # track if local has been written to, if so it may need to be uploaded
         self._dirty = False
 
+    @property
+    def client(self):
+        if getattr(self, "_client", None) is None:
+            self._client = self._cloud_meta.client_class.get_default_client()
+
+        return self._client
+
     def __del__(self) -> None:
         # make sure that file handle to local path is closed
         if self._handle is not None:
             self._handle.close()
 
         # ensure file removed from cache when cloudpath object deleted
-        client = getattr(self, "client", None)
+        client = getattr(self, "_client", None)
         if getattr(client, "file_cache_mode", None) == FileCacheMode.cloudpath_object:
             self.clear_cache()
 
     def __getstate__(self) -> Dict[str, Any]:
         state = self.__dict__.copy()
 
         # don't pickle client
-        del state["client"]
+        del state["_client"]
 
         return state
 
     def __setstate__(self, state: Dict[str, Any]) -> None:
-        client = self._cloud_meta.client_class.get_default_client()
-        state["client"] = client
         self.__dict__.update(state)
 
     @property

tests/test_cloudpath_instantiation.py

@@ -59,6 +59,13 @@ def test_instantiation(rig, path):
         assert str(p._path) == expected.split(":/", 1)[-1]
 
 
+def test_default_client_lazy(rig):
+    cp = rig.path_class(rig.cloud_prefix + "testing/file.txt")
+    assert cp._client is None
+    assert cp.client is not None
+    assert cp._client is not None
+
+
 def test_instantiation_errors(rig):
     with pytest.raises(TypeError):
         rig.path_class()