Add type hints for (NDFrame|Series)._data (#26871)

Author: topper-123

pandas/core/generic.py

@@ -6,7 +6,7 @@
 import operator
 import pickle
 from textwrap import dedent
-from typing import Callable, FrozenSet, List, Set
+from typing import Callable, FrozenSet, List, Optional, Set
 import warnings
 import weakref
 
@@ -35,6 +35,7 @@
 from pandas.core.dtypes.missing import isna, notna
 
 import pandas as pd
+from pandas._typing import Dtype
 from pandas.core import missing, nanops
 import pandas.core.algorithms as algos
 from pandas.core.base import PandasObject, SelectionMixin
@@ -118,12 +119,17 @@ class NDFrame(PandasObject, SelectionMixin):
     ])  # type: FrozenSet[str]
     _metadata = []  # type: List[str]
     _is_copy = None
+    _data = None  # type: BlockManager
 
     # ----------------------------------------------------------------------
     # Constructors
 
-    def __init__(self, data, axes=None, copy=False, dtype=None,
-                 fastpath=False):
+    def __init__(self,
+                 data: BlockManager,
+                 axes: Optional[List[Index]] = None,
+                 copy: bool = False,
+                 dtype: Optional[Dtype] = None,
+                 fastpath: bool = False):
 
         if not fastpath:
             if dtype is not None:

pandas/core/series.py

@@ -142,6 +142,7 @@ class Series(base.IndexOpsMixin, generic.NDFrame):
     # Override cache_readonly bc Series is mutable
     hasnans = property(base.IndexOpsMixin.hasnans.func,
                        doc=base.IndexOpsMixin.hasnans.__doc__)
+    _data = None  # type: SingleBlockManager
 
     # ----------------------------------------------------------------------
     # Constructors