optimised indexing w sliche(None)

dios/indexer.py

@@ -18,6 +18,7 @@ _is_dict_like = dcom.is_dict_like
 _is_number = dcom.is_number
 _is_hashable = dcom.is_hashable
 _is_bool_indexer = ccom.is_bool_indexer
+_is_null_slice = ccom.is_null_slice
 
 
 class _Indexer:
@@ -112,6 +113,10 @@ class _LocIndexer(_Indexer):
         if _is_dios_like(rowkey) or _is_dios_like(colkey):
             raise ValueError("Could not index with multidimensional key")
 
+        # simple optimisation
+        if _is_null_slice(rowkey) and _is_null_slice(colkey):
+            return self.obj.copy()
+
         data = self._data.loc[colkey].copy()
 
         # .loc[any, scalar] -> (a single) series
@@ -180,6 +185,10 @@ class _iLocIndexer(_Indexer):
         if _is_dios_like(rowkey) or _is_dios_like(colkey):
             raise ValueError("Cannot index with multidimensional key")
 
+        # simple optimisation
+        if _is_null_slice(rowkey) and _is_null_slice(colkey):
+            return self.obj.copy()
+
         data = self._data.iloc[colkey].copy()
 
         # .iloc[any, int] -> single series
@@ -240,7 +249,7 @@ class _aLocIndexer(_Indexer):
     """ align Indexer
 
     Automatically align (alignable) indexer on all possible axis,
-    and handle indexing with non-existent or missing keys gratefully.
+    and handle indexing with non-existent or missing keys gracefully.
 
     Also align (alignable) values before setting them with .loc
     """
@@ -390,7 +399,7 @@ class _aLocIndexer(_Indexer):
         elif _is_dios_like(colkey) or _is_nested_list_like(colkey):
             raise ValueError("Could not index with multi-dimensional column key.")
 
-        # handle gratefully: scalar
+        # handle gracefully: scalar
         if _is_hashable(colkey):
             colkey = [colkey] if colkey in self.obj.columns else []
             lowdim = True
@@ -400,6 +409,11 @@ class _aLocIndexer(_Indexer):
             colkey = colkey.values if isinstance(colkey, pd.Series) else colkey
             colkey = self.obj.columns.intersection(colkey)
 
+        # handle gracefully (automatically)
+        # just a simple optimisation
+        elif _is_null_slice(colkey):
+            colkey = self.obj.columns
+
         # not alignable, fall back to .loc (boolean list/series, slice(..), etc.
         else:
             colkey = self._data.loc[colkey].index
@@ -414,11 +428,11 @@ class _aLocIndexer(_Indexer):
         if isinstance(rowkey, pd.Series):
             rowkey = [self._data.at[c].index.intersection(rowkey.index) for c in colkey]
 
-        # handle gratefully: scalar, transform to row-slice
+        # handle gracefully: scalar, transform to row-slice
         elif _is_hashable(rowkey):
             rowkey = [slice(rowkey, rowkey)] * len(colkey)
 
-        # handle gratefully: list-like, filter only existing rows
+        # handle gracefully: list-like, filter only existing rows
         # NOTE: dios.aloc[series.index] is processed here
         elif _is_list_like(rowkey) and not _is_bool_indexer(rowkey):
             rowkey = [self._data.at[c].index.intersection(rowkey) for c in colkey]