Fix type annotations in pandas.core.ops

mypy.ini

@@ -26,9 +26,6 @@ ignore_errors=True
 [mypy-pandas.core.internals.blocks]
 ignore_errors=True
 
-[mypy-pandas.core.ops]
-ignore_errors=True
-
 [mypy-pandas.core.panel]
 ignore_errors=True
 

pandas/core/ops.py

@@ -6,6 +6,7 @@
 import datetime
 import operator
 import textwrap
+from typing import Dict, Optional, Union, cast
 import warnings
 
 import numpy as np
@@ -625,16 +626,21 @@ def _get_op_name(op, special):
            'desc': 'Greater than or equal to',
            'reverse': None,
            'series_examples': None}
-}
+}  # type: Dict[str, Dict[str, Optional[Union[bool, str]]]]
+
+# When TypedDict becomes available, this annotation would be much better and
+# more readable if defined using that structure. The casts() below would not be
+# necessary, because only the dictionary values keyed to 'reversed' would be
+# typed as bool. See GH#26377.
 
 _op_names = list(_op_descriptions.keys())
 for key in _op_names:
     _op_descriptions[key]['reversed'] = False
     reverse_op = _op_descriptions[key]['reverse']
     if reverse_op is not None:
-        _op_descriptions[reverse_op] = _op_descriptions[key].copy()
-        _op_descriptions[reverse_op]['reversed'] = True
-        _op_descriptions[reverse_op]['reverse'] = key
+        _op_descriptions[cast(str, reverse_op)] = _op_descriptions[key].copy()
+        _op_descriptions[cast(str, reverse_op)]['reversed'] = True
+        _op_descriptions[cast(str, reverse_op)]['reverse'] = key
 
 _flex_doc_SERIES = """
 Return {desc} of series and other, element-wise (binary operator `{op_name}`).