ENH: Support plugin DataFrame accessor via entry points (#29076)

Allows external libraries to register DataFrame accessors
using the 'pandas_dataframe_accessor' entry point group.
This enables plugins to be automatically used without
explicit import.

Co-authored-by: Afonso Antunes <[email protected]>

Author: PedroM4rques

pandas/__init__.py

@@ -346,3 +346,7 @@
     "unique",
     "wide_to_long",
 ]
+
+from pandas.core.accessor import DataFrameAccessorLoader
+
+DataFrameAccessorLoader.load()

pandas/core/accessor.py

@@ -26,6 +26,9 @@
     from pandas.core.generic import NDFrame
 
 
+from importlib_metadata import entry_points
+
+
 class DirNamesMixin:
     _accessors: set[str] = set()
     _hidden_attrs: frozenset[str] = frozenset()
@@ -393,3 +396,26 @@ def register_index_accessor(name: str) -> Callable[[TypeT], TypeT]:
     from pandas import Index
 
     return _register_accessor(name, Index)
+
+
+class DataFrameAccessorLoader:
+    """Loader class for registering DataFrame accessors via entry points."""
+
+    ENTRY_POINT_GROUP = "pandas_dataframe_accessor"
+
+    @classmethod
+    def load(cls):
+        """loads and registers accessors defined by 'pandas_dataframe_accessor'."""
+        eps = entry_points(group=cls.ENTRY_POINT_GROUP)
+
+        for ep in eps:
+            name = ep.name
+
+            def make_property(ep):
+                def accessor(self):
+                    cls_ = ep.load()
+                    return cls_(self)
+
+                return accessor
+
+            register_dataframe_accessor(name)(make_property(ep))

pandas/tests/test_plugis_entrypoint_loader.py

@@ -0,0 +1,35 @@
+import pandas as pd
+from pandas.core.accessor import DataFrameAccessorLoader
+
+
+def test_load_dataframe_accessors(monkeypatch):
+    # GH29076
+    # Mocked EntryPoint to simulate a plugin
+    class MockEntryPoint:
+        name = "test_accessor"
+
+        def load(self):
+            class TestAccessor:
+                def __init__(self, df):
+                    self._df = df
+
+                def test_method(self):
+                    return "success"
+
+            return TestAccessor
+
+    # Mock entry_points
+    def mock_entry_points(*, group):
+        if group == DataFrameAccessorLoader.ENTRY_POINT_GROUP:
+            return [MockEntryPoint()]
+        return []
+
+    # Patch entry_points in the correct module
+    monkeypatch.setattr("pandas.core.accessor.entry_points", mock_entry_points)
+
+    DataFrameAccessorLoader.load()
+
+    # Create DataFrame and verify that the accessor was registered
+    df = pd.DataFrame({"a": [1, 2, 3]})
+    assert hasattr(df, "test_accessor")
+    assert df.test_accessor.test_method() == "success"