ENH: Support Plugin Accessors Via Entry Points

doc/source/whatsnew/v3.0.0.rst

@@ -83,6 +83,7 @@ Other enhancements
 - Improved deprecation message for offset aliases (:issue:`60820`)
 - Multiplying two :class:`DateOffset` objects will now raise a ``TypeError`` instead of a ``RecursionError`` (:issue:`59442`)
 - Restore support for reading Stata 104-format and enable reading 103-format dta files (:issue:`58554`)
+- Support :class:`DataFrame`, :class:`Series` and :class:`Index` plugin accessors via entry points (:issue:`29076`)
 - Support passing a :class:`Iterable[Hashable]` input to :meth:`DataFrame.drop_duplicates` (:issue:`59237`)
 - Support reading Stata 102-format (Stata 1) dta files (:issue:`58978`)
 - Support reading Stata 110-format (Stata 7) dta files (:issue:`47176`)

pandas/__init__.py

@@ -346,3 +346,8 @@
     "unique",
     "wide_to_long",
 ]
+
+from .core.accessor import accessor_entry_point_loader
+
+accessor_entry_point_loader()
+del accessor_entry_point_loader

pandas/core/accessor.py

@@ -25,6 +25,11 @@
     from pandas import Index
     from pandas.core.generic import NDFrame
 
+from importlib.metadata import (
+    EntryPoints,
+    entry_points,
+)
+
 
 class DirNamesMixin:
     _accessors: set[str] = set()
@@ -393,3 +398,114 @@ def register_index_accessor(name: str) -> Callable[[TypeT], TypeT]:
     from pandas import Index
 
     return _register_accessor(name, Index)
+
+
+def accessor_entry_point_loader() -> None:
+    """
+    Load and register pandas accessors declared via entry points.
+
+    This function scans the 'pandas.<pd_obj>.accessor' entry point group for
+    accessors registered by third-party packages. Each entry point is expected
+    to follow the format:
+
+        # setup.py
+        entry_points={
+            'pandas.DataFrame.accessor': [ <name> = <module>:<AccessorClass>, ... ],
+            'pandas.Series.accessor':    [ <name> = <module>:<AccessorClass>, ... ],
+            'pandas.Index.accessor':     [ <name> = <module>:<AccessorClass>, ... ],
+        }
+
+    OR for pyproject.toml file:
+
+        # pyproject.toml
+        [project.entry-points."pandas.DataFrame.accessor"]
+        <name> = "<module>:<AccessorClass>"
+
+        [project.entry-points."pandas.Series.accessor"]
+        <name> = "<module>:<AccessorClass>"
+
+        [project.entry-points."pandas.Index.accessor"]
+        <name> = "<module>:<AccessorClass>"
+
+    For more information about entrypoints:
+    https://packaging.python.org/en/latest/guides/creating-and-discovering-plugins/#plugin-entry-points
+
+
+    For each valid entry point:
+    - The accessor class is dynamically imported and registered using
+      the appropriate registration decorator function
+      (e.g. register_dataframe_accessor).
+    - If two packages declare the same accessor name, a warning is issued,
+      and only the first one is used.
+
+    Notes
+    -----
+    - This function is only intended to be called at pandas startup.
+    - For more information about accessors read their documentation.
+
+    Raises
+    ------
+    UserWarning
+        If two accessors share the same name, the second one is ignored.
+
+    Examples
+    --------
+        # setup.py
+        entry_points={
+            'pandas.DataFrame.accessor': [
+                'myplugin = myplugin.accessor:MyPluginAccessor',
+            ],
+        }
+        # END setup.py
+
+        - That entrypoint would allow the following code:
+
+        import pandas as pd
+
+        df = pd.DataFrame({"A": [1, 2, 3]})
+        df.myplugin.do_something() # Calls MyPluginAccessor.do_something()
+    """
+
+    ACCESSOR_REGISTRY_FUNCTIONS: dict[str, Callable] = {
+        "pandas.DataFrame.accessor": register_dataframe_accessor,
+        "pandas.Series.accessor": register_series_accessor,
+        "pandas.Index.accessor": register_index_accessor,
+    }
+
+    pd_objects_entrypoints: list[str] = ACCESSOR_REGISTRY_FUNCTIONS.keys()
+
+    for pd_obj_entrypoint in pd_objects_entrypoints:
+        accessors: EntryPoints = entry_points(group=pd_obj_entrypoint)
+        accessor_package_dict: dict[str, str] = {}
+
+        for new_accessor in accessors:
+            dist = getattr(new_accessor, "dist", None)
+            new_pkg_name = getattr(dist, "name", "Unknown") if dist else "Unknown"
+
+            # Verifies duplicated accessor names
+            if new_accessor.name in accessor_package_dict:
+                loaded_pkg_name: str = accessor_package_dict.get(
+                    new_accessor.name, "Unknown"
+                )
+
+                warnings.warn(
+                    "Warning: you have two accessors with the same name:"
+                    f" '{new_accessor.name}' has already been registered"
+                    f" by the package '{new_pkg_name}'. The "
+                    f"'{new_accessor.name}' provided by the package "
+                    f"'{loaded_pkg_name}' is not being used. "
+                    "Uninstall the package you don't want"
+                    "to use if you want to get rid of this warning.\n",
+                    UserWarning,
+                    stacklevel=2,
+                )
+
+            accessor_package_dict.update({new_accessor.name: new_pkg_name})
+
+            def make_accessor(ep):
+                return lambda self, ep=ep: ep.load()(self)
+
+            register_fn = ACCESSOR_REGISTRY_FUNCTIONS.get(pd_obj_entrypoint)
+
+            if register_fn is not None:
+                register_fn(new_accessor.name)(make_accessor(new_accessor))