REF: simplify _from_mgr constructors, use in more places (#53871)

Author: jbrockmendel

pandas/core/frame.py

@@ -634,23 +634,28 @@ def _constructor(self) -> Callable[..., DataFrame]:
         return DataFrame
 
     def _constructor_from_mgr(self, mgr, axes):
-        if self._constructor is DataFrame:
-            # we are pandas.DataFrame (or a subclass that doesn't override _constructor)
-            return self._from_mgr(mgr, axes=axes)
+        df = self._from_mgr(mgr, axes=axes)
+
+        if type(self) is DataFrame:
+            # fastpath avoiding constructor call
+            return df
         else:
             assert axes is mgr.axes
-            return self._constructor(mgr)
+            return self._constructor(df, copy=False)
 
     _constructor_sliced: Callable[..., Series] = Series
 
     def _sliced_from_mgr(self, mgr, axes) -> Series:
         return Series._from_mgr(mgr, axes)
 
     def _constructor_sliced_from_mgr(self, mgr, axes):
-        if self._constructor_sliced is Series:
-            return self._sliced_from_mgr(mgr, axes)
+        ser = self._sliced_from_mgr(mgr, axes=axes)
+        ser._name = None  # caller is responsible for setting real name
+        if type(self) is DataFrame:
+            # fastpath avoiding constructor call
+            return ser
         assert axes is mgr.axes
-        return self._constructor_sliced(mgr)
+        return self._constructor_sliced(ser, copy=False)
 
     # ----------------------------------------------------------------------
     # Constructors
@@ -11765,12 +11770,10 @@ def isin_(x):
                 )
                 return result.reshape(x.shape)
 
-            res_values = self._mgr.apply(isin_)
-            result = self._constructor(
-                res_values,
-                self.index,
-                self.columns,
-                copy=False,
+            res_mgr = self._mgr.apply(isin_)
+            result = self._constructor_from_mgr(
+                res_mgr,
+                axes=res_mgr.axes,
             )
         return result.__finalize__(self, method="isin")
 

pandas/core/generic.py

@@ -319,7 +319,7 @@ def _as_manager(self, typ: str, copy: bool_t = True) -> Self:
         new_mgr: Manager
         new_mgr = mgr_to_mgr(self._mgr, typ=typ, copy=copy)
         # fastpath of passing a manager doesn't check the option/manager class
-        return self._constructor(new_mgr).__finalize__(self)
+        return self._constructor_from_mgr(new_mgr, axes=new_mgr.axes).__finalize__(self)
 
     @classmethod
     def _from_mgr(cls, mgr: Manager, axes: list[Index]) -> Self:
@@ -6919,7 +6919,7 @@ def _pad_or_backfill(
             inplace=inplace,
             downcast=downcast,
         )
-        result = self._constructor(new_mgr)
+        result = self._constructor_from_mgr(new_mgr, axes=new_mgr.axes)
         if inplace:
             return self._update_inplace(result)
         else:

pandas/core/groupby/groupby.py

@@ -1519,11 +1519,11 @@ def _numba_agg_general(
         aggregator = executor.generate_shared_aggregator(
             func, dtype_mapping, **get_jit_arguments(engine_kwargs)
         )
-        result = sorted_df._mgr.apply(
+        res_mgr = sorted_df._mgr.apply(
             aggregator, start=starts, end=ends, **aggregator_kwargs
         )
-        result.axes[1] = self.grouper.result_index
-        result = df._constructor(result)
+        res_mgr.axes[1] = self.grouper.result_index
+        result = df._constructor_from_mgr(res_mgr, axes=res_mgr.axes)
 
         if data.ndim == 1:
             result = result.squeeze("columns")

pandas/core/reshape/concat.py

@@ -640,7 +640,8 @@ def get_result(self):
 
                 mgr = type(sample._mgr).from_array(res, index=new_index)
 
-                result = cons(mgr, name=name, fastpath=True)
+                result = sample._constructor_from_mgr(mgr, axes=mgr.axes)
+                result._name = name
                 return result.__finalize__(self, method="concat")
 
             # combine as columns in a frame

pandas/core/series.py

@@ -575,12 +575,14 @@ def _constructor(self) -> Callable[..., Series]:
         return Series
 
     def _constructor_from_mgr(self, mgr, axes):
-        if self._constructor is Series:
-            # we are pandas.Series (or a subclass that doesn't override _constructor)
-            return self._from_mgr(mgr, axes=axes)
+        ser = self._from_mgr(mgr, axes=axes)
+        ser._name = None  # caller is responsible for setting real name
+        if type(self) is Series:
+            # fastpath avoiding constructor call
+            return ser
         else:
             assert axes is mgr.axes
-            return self._constructor(mgr)
+            return self._constructor(ser, copy=False)
 
     @property
     def _constructor_expanddim(self) -> Callable[..., DataFrame]:
@@ -599,15 +601,17 @@ def _expanddim_from_mgr(self, mgr, axes) -> DataFrame:
         #  once downstream packages (geopandas) have had a chance to implement
         #  their own overrides.
         # error: "Callable[..., DataFrame]" has no attribute "_from_mgr"  [attr-defined]
-        return self._constructor_expanddim._from_mgr(  # type: ignore[attr-defined]
-            mgr, axes=mgr.axes
-        )
+        from pandas import DataFrame
+
+        return DataFrame._from_mgr(mgr, axes=mgr.axes)
 
     def _constructor_expanddim_from_mgr(self, mgr, axes):
-        if self._constructor is Series:
-            return self._expanddim_from_mgr(mgr, axes)
+        df = self._expanddim_from_mgr(mgr, axes)
+        if type(self) is Series:
+            # fastpath avoiding constructor
+            return df
         assert axes is mgr.axes
-        return self._constructor_expanddim(mgr)
+        return self._constructor_expanddim(df, copy=False)
 
     # types
     @property