Refinements

pandas/core/groupby/groupby.py

@@ -4439,13 +4439,13 @@ def post_processor(
             pass_qs = None
 
         ids, ngroups = self.grouper.group_info
-        # TODO: Is this hit?
-        ids = ids[ids >= 0]
+        if self.dropna:
+            ids = ids[ids >= 0]
         nqs = len(qs)
 
         func = partial(
             libgroupby.group_quantile,
-            labels=ids[ids >= 0],
+            labels=ids,
             qs=qs,
             interpolation=interpolation,
             starts=starts,

pandas/core/groupby/grouper.py

@@ -735,10 +735,6 @@ def _codes_and_uniques(self) -> tuple[npt.NDArray[np.signedinteger], ArrayLike]:
                         codes = np.where(codes >= na_code, codes + 1, codes)
                         codes = np.where(na_mask, na_code, codes)
 
-            # TODO: Can this be removed?
-            if not self._observed:
-                uniques = uniques.reorder_categories(self._orig_cats)
-
             return codes, uniques
 
         elif isinstance(self.grouping_vector, ops.BaseGrouper):
@@ -998,9 +994,7 @@ def is_in_obj(gpr) -> bool:
         groupings.append(Grouping(Index([], dtype="int"), np.array([], dtype=np.intp)))
 
     # create the internals grouper
-    grouper = ops.BaseGrouper(
-        group_axis, groupings, sort=sort, dropna=dropna, observed=observed
-    )
+    grouper = ops.BaseGrouper(group_axis, groupings, sort=sort, dropna=dropna)
     return grouper, frozenset(exclusions), obj
 
 

pandas/core/groupby/ops.py

@@ -579,16 +579,13 @@ def __init__(
         groupings: Sequence[grouper.Grouping],
         sort: bool = True,
         dropna: bool = True,
-        # TODO: Is this still needed?
-        observed: bool = True,
     ) -> None:
         assert isinstance(axis, Index), axis
 
         self.axis = axis
         self._groupings: list[grouper.Grouping] = list(groupings)
         self._sort = sort
         self.dropna = dropna
-        self.observed = observed
 
     @property
     def groupings(self) -> list[grouper.Grouping]:
@@ -859,7 +856,6 @@ def result_index_and_ids(self) -> tuple[Index, np.ndarray]:
 
         return result_index, ids
 
-    # TODO: How is this different from .levels?
     @final
     def get_group_levels(self) -> list[Index]:
         # Note: only called from _insert_inaxis_grouper, which