PERF: Eliminate circular references in accessor attributes

doc/source/whatsnew/v3.0.0.rst

@@ -335,6 +335,7 @@ Removal of prior version deprecations/changes
 
 Performance improvements
 ~~~~~~~~~~~~~~~~~~~~~~~~
+- Eliminated circular reference in to original pandas object in accessor attributes (e.g. :attr:`Series.str`). However, accessor instantiation is no longer cached (:issue:`47667`, :issue:`41357`)
 - :attr:`Categorical.categories` returns a :class:`RangeIndex` columns instead of an :class:`Index` if the constructed ``values`` was a ``range``. (:issue:`57787`)
 - :class:`DataFrame` returns a :class:`RangeIndex` columns when possible when ``data`` is a ``dict`` (:issue:`57943`)
 - :class:`Series` returns a :class:`RangeIndex` index when possible when ``data`` is a ``dict`` (:issue:`58118`)

pandas/core/accessor.py

@@ -195,17 +195,11 @@ def add_delegate_accessors(cls):
     return add_delegate_accessors
 
 
-# Ported with modifications from xarray; licence at LICENSES/XARRAY_LICENSE
-# https://github.com/pydata/xarray/blob/master/xarray/core/extensions.py
-# 1. We don't need to catch and re-raise AttributeErrors as RuntimeErrors
-# 2. We use a UserWarning instead of a custom Warning
-
-
-class CachedAccessor:
+class Accessor:
     """
     Custom property-like object.
 
-    A descriptor for caching accessors.
+    A descriptor for accessors.
 
     Parameters
     ----------
@@ -229,13 +223,7 @@ def __get__(self, obj, cls):
         if obj is None:
             # we're accessing the attribute of the class, i.e., Dataset.geo
             return self._accessor
-        accessor_obj = self._accessor(obj)
-        # Replace the property with the accessor object. Inspired by:
-        # https://www.pydanny.com/cached-property.html
-        # We need to use object.__setattr__ because we overwrite __setattr__ on
-        # NDFrame
-        object.__setattr__(obj, self._name, accessor_obj)
-        return accessor_obj
+        return self._accessor(obj)
 
 
 @doc(klass="", examples="", others="")
@@ -295,7 +283,7 @@ def decorator(accessor: TypeT) -> TypeT:
                 UserWarning,
                 stacklevel=find_stack_level(),
             )
-        setattr(cls, name, CachedAccessor(name, accessor))
+        setattr(cls, name, Accessor(name, accessor))
         cls._accessors.add(name)
         return accessor
 

pandas/core/frame.py

@@ -125,7 +125,7 @@
     ops,
     roperator,
 )
-from pandas.core.accessor import CachedAccessor
+from pandas.core.accessor import Accessor
 from pandas.core.apply import reconstruct_and_relabel_result
 from pandas.core.array_algos.take import take_2d_multi
 from pandas.core.arraylike import OpsMixin
@@ -13487,10 +13487,10 @@ def isin_(x):
 
     # ----------------------------------------------------------------------
     # Add plotting methods to DataFrame
-    plot = CachedAccessor("plot", pandas.plotting.PlotAccessor)
+    plot = Accessor("plot", pandas.plotting.PlotAccessor)
     hist = pandas.plotting.hist_frame
     boxplot = pandas.plotting.boxplot_frame
-    sparse = CachedAccessor("sparse", SparseFrameAccessor)
+    sparse = Accessor("sparse", SparseFrameAccessor)
 
     # ----------------------------------------------------------------------
     # Internal Interface Methods

pandas/core/indexes/base.py

@@ -142,7 +142,7 @@
     nanops,
     ops,
 )
-from pandas.core.accessor import CachedAccessor
+from pandas.core.accessor import Accessor
 import pandas.core.algorithms as algos
 from pandas.core.array_algos.putmask import (
     setitem_datetimelike_compat,
@@ -462,7 +462,7 @@ def _engine_type(
 
     _accessors = {"str"}
 
-    str = CachedAccessor("str", StringMethods)
+    str = Accessor("str", StringMethods)
 
     _references = None
 

pandas/core/series.py

@@ -101,7 +101,7 @@
     ops,
     roperator,
 )
-from pandas.core.accessor import CachedAccessor
+from pandas.core.accessor import Accessor
 from pandas.core.apply import SeriesApply
 from pandas.core.arrays import ExtensionArray
 from pandas.core.arrays.arrow import (
@@ -5754,13 +5754,13 @@ def to_period(
     # ----------------------------------------------------------------------
     # Accessor Methods
     # ----------------------------------------------------------------------
-    str = CachedAccessor("str", StringMethods)
-    dt = CachedAccessor("dt", CombinedDatetimelikeProperties)
-    cat = CachedAccessor("cat", CategoricalAccessor)
-    plot = CachedAccessor("plot", pandas.plotting.PlotAccessor)
-    sparse = CachedAccessor("sparse", SparseAccessor)
-    struct = CachedAccessor("struct", StructAccessor)
-    list = CachedAccessor("list", ListAccessor)
+    str = Accessor("str", StringMethods)
+    dt = Accessor("dt", CombinedDatetimelikeProperties)
+    cat = Accessor("cat", CategoricalAccessor)
+    plot = Accessor("plot", pandas.plotting.PlotAccessor)
+    sparse = Accessor("sparse", SparseAccessor)
+    struct = Accessor("struct", StructAccessor)
+    list = Accessor("list", ListAccessor)
 
     # ----------------------------------------------------------------------
     # Add plotting methods to Series

pandas/tests/strings/test_api.py

@@ -1,3 +1,5 @@
+import weakref
+
 import numpy as np
 import pytest
 
@@ -68,6 +70,15 @@ def test_api(any_string_dtype):
     assert isinstance(Series([""], dtype=any_string_dtype).str, StringMethods)
 
 
+def test_no_circular_reference(any_string_dtype):
+    # GH 47667
+    ser = Series([""], dtype=any_string_dtype)
+    ref = weakref.ref(ser)
+    ser.str  # Used to cache and cause circular reference
+    del ser
+    assert ref() is None
+
+
 def test_api_mi_raises():
     # GH 23679
     mi = MultiIndex.from_arrays([["a", "b", "c"]])

pandas/tests/test_register_accessor.py

@@ -1,5 +1,6 @@
 from collections.abc import Generator
 import contextlib
+import weakref
 
 import pytest
 
@@ -101,3 +102,22 @@ def __init__(self, data) -> None:
 
         with pytest.raises(AttributeError, match="whoops"):
             pd.Series([], dtype=object).bad
+
+
+@pytest.mark.parametrize(
+    "klass, registrar",
+    [
+        (pd.Series, pd.api.extensions.register_series_accessor),
+        (pd.DataFrame, pd.api.extensions.register_dataframe_accessor),
+        (pd.Index, pd.api.extensions.register_index_accessor),
+    ],
+)
+def test_no_circular_reference(klass, registrar):
+    # GH 41357
+    with ensure_removed(klass, "access"):
+        registrar("access")(MyAccessor)
+        obj = klass([0])
+        ref = weakref.ref(obj)
+        assert obj.access.obj is obj
+        del obj
+        assert ref() is None