more changes

Author: topper-123

pandas/core/groupby/grouper.py

@@ -3,11 +3,12 @@
 split-apply-combine paradigm.
 """
 
-from typing import Tuple
+from typing import Optional, Tuple
 import warnings
 
 import numpy as np
 
+from pandas._typing import FrameOrSeries
 from pandas.util._decorators import cache_readonly
 
 from pandas.core.dtypes.common import (
@@ -228,7 +229,7 @@ class Grouping:
     ----------
     index : Index
     grouper :
-    obj :
+    obj Union[DataFrame, Series]:
     name :
     level :
     observed : bool, default False
@@ -247,16 +248,15 @@ class Grouping:
 
     def __init__(
         self,
-        index,
+        index: Index,
         grouper=None,
-        obj=None,
+        obj: Optional[FrameOrSeries] = None,
         name=None,
         level=None,
-        sort=True,
-        observed=False,
-        in_axis=False,
+        sort: bool = True,
+        observed: bool = False,
+        in_axis: bool = False,
     ):
-
         self.name = name
         self.level = level
         self.grouper = _convert_grouper(index, grouper)
@@ -306,7 +306,7 @@ def __init__(
             self.grouper = grouper._get_grouper()
 
         else:
-            if self.grouper is None and self.name is not None:
+            if self.grouper is None and self.name is not None and self.obj is not None:
                 self.grouper = self.obj[self.name]
 
             elif isinstance(self.grouper, (list, tuple)):
@@ -676,7 +676,7 @@ def _is_label_like(val):
     return isinstance(val, (str, tuple)) or (val is not None and is_scalar(val))
 
 
-def _convert_grouper(axis, grouper):
+def _convert_grouper(axis: Index, grouper):
     if isinstance(grouper, dict):
         return grouper.get
     elif isinstance(grouper, Series):

pandas/core/groupby/ops.py

@@ -7,7 +7,7 @@
 """
 
 import collections
-from typing import List, Optional, Type
+from typing import List, Optional, Type, Sequence
 
 import numpy as np
 
@@ -41,7 +41,7 @@
 import pandas.core.common as com
 from pandas.core.frame import DataFrame
 from pandas.core.generic import NDFrame
-from pandas.core.groupby import base
+from pandas.core.groupby import base, grouper
 from pandas.core.index import Index, MultiIndex, ensure_index
 from pandas.core.series import Series
 from pandas.core.sorting import (
@@ -62,13 +62,13 @@ class BaseGrouper:
     Parameters
     ----------
     axis : Index
-    groupings : array of grouping
+    groupings : Sequence[Grouping]
         all the grouping instances to handle in this grouper
         for example for grouper list to groupby, need to pass the list
-    sort : boolean, default True
+    sort : bool, default True
         whether this grouper will give sorted result or not
-    group_keys : boolean, default True
-    mutated : boolean, default False
+    group_keys : bool, default True
+    mutated : bool, default False
     indexer : intp array, optional
         the indexer created by Grouper
         some groupers (TimeGrouper) will sort its axis and its
@@ -77,18 +77,18 @@ class BaseGrouper:
     """
 
     def __init__(
-        self,
-        axis: Index,
-        groupings,
-        sort=True,
-        group_keys=True,
-        mutated=False,
-        indexer=None,
-    ):
+            self,
+            axis: Index,
+            groupings: 'Sequence[grouper.Grouping]',
+            sort: bool = True,
+            group_keys: bool = True,
+            mutated : bool = False,
+            indexer: Optional[np.ndarray] = None):
         assert isinstance(axis, Index), axis
+
         self._filter_empty_groups = self.compressed = len(groupings) != 1
         self.axis = axis
-        self.groupings = groupings
+        self.groupings = groupings  # type: Sequence[grouper.Grouping]
         self.sort = sort
         self.group_keys = group_keys
         self.mutated = mutated