Add docs

phofl · Sep 7, 2023 · de02cb0 · de02cb0
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diff --git a/doc/source/reference/extensions.rst b/doc/source/reference/extensions.rst
@@ -34,6 +34,7 @@ objects.
 
       api.extensions.ExtensionArray._accumulate
       api.extensions.ExtensionArray._concat_same_type
+      api.extensions.ExtensionArray._factorize_with_other_for_merge
       api.extensions.ExtensionArray._formatter
       api.extensions.ExtensionArray._from_factorized
       api.extensions.ExtensionArray._from_sequence

diff --git a/pandas/core/arrays/base.py b/pandas/core/arrays/base.py
@@ -2270,6 +2270,20 @@ def _groupby_op(
     def _factorize_with_other_for_merge(
         self, other: Self, sort: bool = False
     ) -> tuple[npt.NDArray[np.intp], npt.NDArray[np.intp], int]:
+        """Factorizes two arrays to get codes for merge operations.
+
+        This allows extension array authors to implement efficient factorizations
+        for merge operations.
+
+        Parameters
+        ----------
+        other : ExtensionArray with the same dtype as self.
+        sort : Whether to sort the result.
+
+        Returns
+        -------
+        tuple of codes for left and right and the number of unique elements.
+        """
         lk, _ = self._values_for_factorize()
         rk, _ = other._values_for_factorize()
         return factorize_arrays(lk, rk, sort)