From f93f9f37a4ab8926f535094ba59595864c1d8ff0 Mon Sep 17 00:00:00 2001
From: Marco Gorelli <marcogorelli@protonmail.com>
Date: Fri, 24 Jun 2022 20:06:27 +0200
Subject: [PATCH 1/2] add some -> to pandas core

---
 pandas/core/array_algos/replace.py        |  2 +-
 pandas/core/array_algos/take.py           |  8 ++++----
 pandas/core/arrays/_mixins.py             |  2 +-
 pandas/core/arrays/arrow/_arrow_utils.py  |  2 +-
 pandas/core/arrays/base.py                |  6 +++---
 pandas/core/arrays/categorical.py         | 12 ++++++------
 pandas/core/arrays/datetimelike.py        |  6 +++---
 pandas/core/arrays/datetimes.py           |  2 +-
 pandas/core/arrays/interval.py            |  4 ++--
 pandas/core/arrays/period.py              |  2 +-
 pandas/core/arrays/sparse/accessor.py     |  4 ++--
 pandas/core/arrays/sparse/array.py        |  8 ++++----
 pandas/core/arrays/sparse/dtype.py        |  2 +-
 pandas/core/arrays/sparse/scipy_sparse.py |  2 +-
 pandas/core/arrays/string_.py             |  4 ++--
 pandas/core/arrays/timedeltas.py          |  2 +-
 pandas/core/base.py                       |  4 ++--
 pandas/core/common.py                     |  6 ++++--
 pandas/core/computation/eval.py           |  8 ++++----
 pandas/core/computation/expressions.py    |  4 ++--
 pandas/core/computation/ops.py            |  8 ++++----
 pandas/core/computation/pytables.py       |  4 ++--
 pandas/core/config_init.py                | 18 +++++++++---------
 pandas/core/dtypes/cast.py                |  4 ++--
 pandas/core/dtypes/dtypes.py              |  4 ++--
 pandas/core/dtypes/missing.py             |  2 +-
 pandas/core/flags.py                      |  4 ++--
 pandas/core/frame.py                      |  4 ++--
 pandas/core/generic.py                    |  8 ++++----
 pandas/core/groupby/grouper.py            |  2 +-
 pandas/core/groupby/ops.py                |  2 +-
 pandas/core/indexes/base.py               | 14 +++++++-------
 pandas/core/indexes/extension.py          |  2 +-
 pandas/core/indexes/multi.py              |  2 +-
 pandas/core/indexes/range.py              |  2 +-
 pandas/core/indexing.py                   | 22 ++++++++++++----------
 pandas/core/internals/array_manager.py    |  6 +++---
 pandas/core/internals/blocks.py           |  4 ++--
 pandas/core/internals/concat.py           |  2 +-
 pandas/core/internals/managers.py         |  8 ++++----
 pandas/core/internals/ops.py              |  2 +-
 pandas/core/missing.py                    |  2 +-
 pandas/core/ops/array_ops.py              |  2 +-
 pandas/core/ops/invalid.py                |  2 +-
 pandas/core/ops/mask_ops.py               |  2 +-
 pandas/core/ops/methods.py                |  4 ++--
 pandas/core/reshape/concat.py             |  2 +-
 pandas/core/reshape/encoding.py           |  2 +-
 pandas/core/reshape/reshape.py            |  2 +-
 pandas/core/series.py                     |  4 ++--
 pandas/core/window/ewm.py                 |  2 +-
 pandas/core/window/online.py              |  2 +-
 pandas/core/window/rolling.py             | 10 +++++-----
 53 files changed, 127 insertions(+), 123 deletions(-)

diff --git a/pandas/core/array_algos/replace.py b/pandas/core/array_algos/replace.py
index 19a44dbfe6f6d..1192191512e10 100644
--- a/pandas/core/array_algos/replace.py
+++ b/pandas/core/array_algos/replace.py
@@ -67,7 +67,7 @@ def compare_or_regex_search(
 
     def _check_comparison_types(
         result: ArrayLike | bool, a: ArrayLike, b: Scalar | Pattern
-    ):
+    ) -> None:
         """
         Raises an error if the two arrays (a,b) cannot be compared.
         Otherwise, returns the comparison result as expected.
diff --git a/pandas/core/array_algos/take.py b/pandas/core/array_algos/take.py
index 188725f003f1e..6f7d7d85c4f2c 100644
--- a/pandas/core/array_algos/take.py
+++ b/pandas/core/array_algos/take.py
@@ -337,7 +337,7 @@ def _get_take_nd_function(
 
     if func is None:
 
-        def func(arr, indexer, out, fill_value=np.nan):
+        def func(arr, indexer, out, fill_value=np.nan) -> None:
             indexer = ensure_platform_int(indexer)
             _take_nd_object(
                 arr, indexer, out, axis=axis, fill_value=fill_value, mask_info=mask_info
@@ -349,7 +349,7 @@ def func(arr, indexer, out, fill_value=np.nan):
 def _view_wrapper(f, arr_dtype=None, out_dtype=None, fill_wrap=None):
     def wrapper(
         arr: np.ndarray, indexer: np.ndarray, out: np.ndarray, fill_value=np.nan
-    ):
+    ) -> None:
         if arr_dtype is not None:
             arr = arr.view(arr_dtype)
         if out_dtype is not None:
@@ -364,7 +364,7 @@ def wrapper(
 def _convert_wrapper(f, conv_dtype):
     def wrapper(
         arr: np.ndarray, indexer: np.ndarray, out: np.ndarray, fill_value=np.nan
-    ):
+    ) -> None:
         if conv_dtype == object:
             # GH#39755 avoid casting dt64/td64 to integers
             arr = ensure_wrapped_if_datetimelike(arr)
@@ -506,7 +506,7 @@ def _take_nd_object(
     axis: int,
     fill_value,
     mask_info,
-):
+) -> None:
     if mask_info is not None:
         mask, needs_masking = mask_info
     else:
diff --git a/pandas/core/arrays/_mixins.py b/pandas/core/arrays/_mixins.py
index b15e0624963ea..45bd1c583f4d5 100644
--- a/pandas/core/arrays/_mixins.py
+++ b/pandas/core/arrays/_mixins.py
@@ -259,7 +259,7 @@ def _validate_shift_value(self, fill_value):
         #  we can remove this and use validate_fill_value directly
         return self._validate_scalar(fill_value)
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key, value) -> None:
         key = check_array_indexer(self, key)
         value = self._validate_setitem_value(value)
         self._ndarray[key] = value
diff --git a/pandas/core/arrays/arrow/_arrow_utils.py b/pandas/core/arrays/arrow/_arrow_utils.py
index e0f242e2ced5d..ac7e31339e37b 100644
--- a/pandas/core/arrays/arrow/_arrow_utils.py
+++ b/pandas/core/arrays/arrow/_arrow_utils.py
@@ -14,7 +14,7 @@
 from pandas.core.arrays.interval import VALID_CLOSED
 
 
-def fallback_performancewarning(version: str | None = None):
+def fallback_performancewarning(version: str | None = None) -> None:
     """
     Raise a PerformanceWarning for falling back to ExtensionArray's
     non-pyarrow method
diff --git a/pandas/core/arrays/base.py b/pandas/core/arrays/base.py
index eb3c6d6d26101..1484e656e8082 100644
--- a/pandas/core/arrays/base.py
+++ b/pandas/core/arrays/base.py
@@ -1656,7 +1656,7 @@ def _create_arithmetic_method(cls, op):
         raise AbstractMethodError(cls)
 
     @classmethod
-    def _add_arithmetic_ops(cls):
+    def _add_arithmetic_ops(cls) -> None:
         setattr(cls, "__add__", cls._create_arithmetic_method(operator.add))
         setattr(cls, "__radd__", cls._create_arithmetic_method(roperator.radd))
         setattr(cls, "__sub__", cls._create_arithmetic_method(operator.sub))
@@ -1681,7 +1681,7 @@ def _create_comparison_method(cls, op):
         raise AbstractMethodError(cls)
 
     @classmethod
-    def _add_comparison_ops(cls):
+    def _add_comparison_ops(cls) -> None:
         setattr(cls, "__eq__", cls._create_comparison_method(operator.eq))
         setattr(cls, "__ne__", cls._create_comparison_method(operator.ne))
         setattr(cls, "__lt__", cls._create_comparison_method(operator.lt))
@@ -1694,7 +1694,7 @@ def _create_logical_method(cls, op):
         raise AbstractMethodError(cls)
 
     @classmethod
-    def _add_logical_ops(cls):
+    def _add_logical_ops(cls) -> None:
         setattr(cls, "__and__", cls._create_logical_method(operator.and_))
         setattr(cls, "__rand__", cls._create_logical_method(roperator.rand_))
         setattr(cls, "__or__", cls._create_logical_method(operator.or_))
diff --git a/pandas/core/arrays/categorical.py b/pandas/core/arrays/categorical.py
index 70699c45e0c36..ddc70889ba607 100644
--- a/pandas/core/arrays/categorical.py
+++ b/pandas/core/arrays/categorical.py
@@ -738,7 +738,7 @@ def categories(self):
         return self.dtype.categories
 
     @categories.setter
-    def categories(self, categories):
+    def categories(self, categories) -> None:
         new_dtype = CategoricalDtype(categories, ordered=self.ordered)
         if self.dtype.categories is not None and len(self.dtype.categories) != len(
             new_dtype.categories
@@ -776,7 +776,7 @@ def codes(self) -> np.ndarray:
         v.flags.writeable = False
         return v
 
-    def _set_categories(self, categories, fastpath=False):
+    def _set_categories(self, categories, fastpath=False) -> None:
         """
         Sets new categories inplace
 
@@ -1700,7 +1700,7 @@ def _internal_get_values(self):
             return self.categories.astype("object").take(self._codes, fill_value=np.nan)
         return np.array(self)
 
-    def check_for_ordered(self, op):
+    def check_for_ordered(self, op) -> None:
         """assert that we are ordered"""
         if not self.ordered:
             raise TypeError(
@@ -1931,7 +1931,7 @@ def _codes(self) -> np.ndarray:
         return self._ndarray
 
     @_codes.setter
-    def _codes(self, value: np.ndarray):
+    def _codes(self, value: np.ndarray) -> None:
         warn(
             "Setting the codes on a Categorical is deprecated and will raise in "
             "a future version. Create a new Categorical object instead",
@@ -1985,7 +1985,7 @@ def __contains__(self, key) -> bool:
     # ------------------------------------------------------------------
     # Rendering Methods
 
-    def _formatter(self, boxed: bool = False):
+    def _formatter(self, boxed: bool = False) -> None:
         # Defer to CategoricalFormatter's formatter.
         return None
 
@@ -2713,7 +2713,7 @@ def __init__(self, data) -> None:
         self._freeze()
 
     @staticmethod
-    def _validate(data):
+    def _validate(data) -> None:
         if not is_categorical_dtype(data.dtype):
             raise AttributeError("Can only use .cat accessor with a 'category' dtype")
 
diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index f7de291f83d03..ee2d5b5560843 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -410,7 +410,7 @@ def __setitem__(  # type: ignore[override]
 
         self._maybe_clear_freq()
 
-    def _maybe_clear_freq(self):
+    def _maybe_clear_freq(self) -> None:
         # inplace operations like __setitem__ may invalidate the freq of
         # DatetimeArray and TimedeltaArray
         pass
@@ -924,7 +924,7 @@ def freq(self):
         return self._freq
 
     @freq.setter
-    def freq(self, value):
+    def freq(self, value) -> None:
         if value is not None:
             value = to_offset(value)
             self._validate_frequency(self, value)
@@ -976,7 +976,7 @@ def resolution(self) -> str:
         return self._resolution_obj.attrname  # type: ignore[union-attr]
 
     @classmethod
-    def _validate_frequency(cls, index, freq, **kwargs):
+    def _validate_frequency(cls, index, freq, **kwargs) -> None:
         """
         Validate that a frequency is compatible with the values of a given
         Datetime Array/Index or Timedelta Array/Index
diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py
index 5f060542526d3..80ae7bbedd4ff 100644
--- a/pandas/core/arrays/datetimes.py
+++ b/pandas/core/arrays/datetimes.py
@@ -520,7 +520,7 @@ def _unbox_scalar(self, value, setitem: bool = False) -> np.datetime64:
     def _scalar_from_string(self, value) -> Timestamp | NaTType:
         return Timestamp(value, tz=self.tz)
 
-    def _check_compatible_with(self, other, setitem: bool = False):
+    def _check_compatible_with(self, other, setitem: bool = False) -> None:
         if other is NaT:
             return
         self._assert_tzawareness_compat(other)
diff --git a/pandas/core/arrays/interval.py b/pandas/core/arrays/interval.py
index 1015a54826ac8..0e1a294b282e4 100644
--- a/pandas/core/arrays/interval.py
+++ b/pandas/core/arrays/interval.py
@@ -598,7 +598,7 @@ def from_tuples(
 
         return cls.from_arrays(left, right, inclusive, copy=False, dtype=dtype)
 
-    def _validate(self):
+    def _validate(self) -> None:
         """
         Verify that the IntervalArray is valid.
 
@@ -692,7 +692,7 @@ def __getitem__(
             raise ValueError("multi-dimensional indexing not allowed")
         return self._shallow_copy(left, right)
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key, value) -> None:
         value_left, value_right = self._validate_setitem_value(value)
         key = check_array_indexer(self, key)
 
diff --git a/pandas/core/arrays/period.py b/pandas/core/arrays/period.py
index 291810c5db2f9..09ec01ddbb26a 100644
--- a/pandas/core/arrays/period.py
+++ b/pandas/core/arrays/period.py
@@ -336,7 +336,7 @@ def _unbox_scalar(  # type: ignore[override]
     def _scalar_from_string(self, value: str) -> Period:
         return Period(value, freq=self.freq)
 
-    def _check_compatible_with(self, other, setitem: bool = False):
+    def _check_compatible_with(self, other, setitem: bool = False) -> None:
         if other is NaT:
             return
         self._require_matching_freq(other)
diff --git a/pandas/core/arrays/sparse/accessor.py b/pandas/core/arrays/sparse/accessor.py
index 41af7d4ccd506..0fb8b4413b1d2 100644
--- a/pandas/core/arrays/sparse/accessor.py
+++ b/pandas/core/arrays/sparse/accessor.py
@@ -33,7 +33,7 @@ class SparseAccessor(BaseAccessor, PandasDelegate):
     Accessor for SparseSparse from other sparse matrix data types.
     """
 
-    def _validate(self, data):
+    def _validate(self, data) -> None:
         if not isinstance(data.dtype, SparseDtype):
             raise AttributeError(self._validation_msg)
 
@@ -222,7 +222,7 @@ class SparseFrameAccessor(BaseAccessor, PandasDelegate):
     .. versionadded:: 0.25.0
     """
 
-    def _validate(self, data):
+    def _validate(self, data) -> None:
         dtypes = data.dtypes
         if not all(isinstance(t, SparseDtype) for t in dtypes):
             raise AttributeError(self._validation_msg)
diff --git a/pandas/core/arrays/sparse/array.py b/pandas/core/arrays/sparse/array.py
index 0c34229fb5080..c51864bce2236 100644
--- a/pandas/core/arrays/sparse/array.py
+++ b/pandas/core/arrays/sparse/array.py
@@ -605,7 +605,7 @@ def __array__(self, dtype: NpDtype | None = None) -> np.ndarray:
         out[self.sp_index.indices] = self.sp_values
         return out
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key, value) -> None:
         # I suppose we could allow setting of non-fill_value elements.
         # TODO(SparseArray.__setitem__): remove special cases in
         # ExtensionBlock.where
@@ -657,7 +657,7 @@ def fill_value(self):
         return self.dtype.fill_value
 
     @fill_value.setter
-    def fill_value(self, value):
+    def fill_value(self, value) -> None:
         self._dtype = SparseDtype(self.dtype.subtype, value)
 
     @property
@@ -1381,7 +1381,7 @@ def _where(self, mask, value):
     # ------------------------------------------------------------------------
     # IO
     # ------------------------------------------------------------------------
-    def __setstate__(self, state):
+    def __setstate__(self, state) -> None:
         """Necessary for making this object picklable"""
         if isinstance(state, tuple):
             # Compat for pandas < 0.24.0
@@ -1795,7 +1795,7 @@ def __repr__(self) -> str:
         pp_index = printing.pprint_thing(self.sp_index)
         return f"{pp_str}\nFill: {pp_fill}\n{pp_index}"
 
-    def _formatter(self, boxed=False):
+    def _formatter(self, boxed=False) -> None:
         # Defer to the formatter from the GenericArrayFormatter calling us.
         # This will infer the correct formatter from the dtype of the values.
         return None
diff --git a/pandas/core/arrays/sparse/dtype.py b/pandas/core/arrays/sparse/dtype.py
index b6bb5faeebdee..652c9f3020759 100644
--- a/pandas/core/arrays/sparse/dtype.py
+++ b/pandas/core/arrays/sparse/dtype.py
@@ -148,7 +148,7 @@ def fill_value(self):
         """
         return self._fill_value
 
-    def _check_fill_value(self):
+    def _check_fill_value(self) -> None:
         if not is_scalar(self._fill_value):
             raise ValueError(
                 f"fill_value must be a scalar. Got {self._fill_value} instead"
diff --git a/pandas/core/arrays/sparse/scipy_sparse.py b/pandas/core/arrays/sparse/scipy_sparse.py
index 88e1778d4c854..efe5ffb416a2e 100644
--- a/pandas/core/arrays/sparse/scipy_sparse.py
+++ b/pandas/core/arrays/sparse/scipy_sparse.py
@@ -28,7 +28,7 @@
     import scipy.sparse
 
 
-def _check_is_partition(parts: Iterable, whole: Iterable):
+def _check_is_partition(parts: Iterable, whole: Iterable) -> None:
     whole = set(whole)
     parts = [set(x) for x in parts]
     if set.intersection(*parts) != set():
diff --git a/pandas/core/arrays/string_.py b/pandas/core/arrays/string_.py
index 45683d83a1303..8880ea6ef5935 100644
--- a/pandas/core/arrays/string_.py
+++ b/pandas/core/arrays/string_.py
@@ -304,7 +304,7 @@ def __init__(self, values, copy=False) -> None:
             self._validate()
         NDArrayBacked.__init__(self, self._ndarray, StringDtype(storage="python"))
 
-    def _validate(self):
+    def _validate(self) -> None:
         """Validate that we only store NA or strings."""
         if len(self._ndarray) and not lib.is_string_array(self._ndarray, skipna=True):
             raise ValueError("StringArray requires a sequence of strings or pandas.NA")
@@ -379,7 +379,7 @@ def _values_for_factorize(self):
         arr[mask] = -1
         return arr, -1
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key, value) -> None:
         value = extract_array(value, extract_numpy=True)
         if isinstance(value, type(self)):
             # extract_array doesn't extract PandasArray subclasses
diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index e08518a54fe6b..5902aecf263f3 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -439,7 +439,7 @@ def _format_native_types(
     # ----------------------------------------------------------------
     # Arithmetic Methods
 
-    def _add_offset(self, other):
+    def _add_offset(self, other) -> None:
         assert not isinstance(other, Tick)
         raise TypeError(
             f"cannot add the type {type(other).__name__} to a {type(self).__name__}"
diff --git a/pandas/core/base.py b/pandas/core/base.py
index b4c2c81ee666f..a4931c7505cf8 100644
--- a/pandas/core/base.py
+++ b/pandas/core/base.py
@@ -154,14 +154,14 @@ class NoNewAttributesMixin:
     `object.__setattr__(self, key, value)`.
     """
 
-    def _freeze(self):
+    def _freeze(self) -> None:
         """
         Prevents setting additional attributes.
         """
         object.__setattr__(self, "__frozen", True)
 
     # prevent adding any attribute via s.xxx.new_attribute = ...
-    def __setattr__(self, key: str, value):
+    def __setattr__(self, key: str, value) -> None:
         # _cache is used by a decorator
         # We need to check both 1.) cls.__dict__ and 2.) getattr(self, key)
         # because
diff --git a/pandas/core/common.py b/pandas/core/common.py
index 707201153e44a..980e7a79414ba 100644
--- a/pandas/core/common.py
+++ b/pandas/core/common.py
@@ -553,7 +553,7 @@ def temp_setattr(obj, attr: str, value) -> Iterator[None]:
         setattr(obj, attr, old_value)
 
 
-def require_length_match(data, index: Index):
+def require_length_match(data, index: Index) -> None:
     """
     Check the length of data matches the length of the index.
     """
@@ -665,7 +665,9 @@ def resolve_numeric_only(numeric_only: bool | None | lib.NoDefault) -> bool:
     return result
 
 
-def deprecate_numeric_only_default(cls: type, name: str, deprecate_none: bool = False):
+def deprecate_numeric_only_default(
+    cls: type, name: str, deprecate_none: bool = False
+) -> None:
     """Emit FutureWarning message for deprecation of numeric_only.
 
     See GH#46560 for details on the deprecation.
diff --git a/pandas/core/computation/eval.py b/pandas/core/computation/eval.py
index d82cc37b90ad4..9e3f2849a6b40 100644
--- a/pandas/core/computation/eval.py
+++ b/pandas/core/computation/eval.py
@@ -67,7 +67,7 @@ def _check_engine(engine: str | None) -> str:
     return engine
 
 
-def _check_parser(parser: str):
+def _check_parser(parser: str) -> None:
     """
     Make sure a valid parser is passed.
 
@@ -86,7 +86,7 @@ def _check_parser(parser: str):
         )
 
 
-def _check_resolvers(resolvers):
+def _check_resolvers(resolvers) -> None:
     if resolvers is not None:
         for resolver in resolvers:
             if not hasattr(resolver, "__getitem__"):
@@ -97,7 +97,7 @@ def _check_resolvers(resolvers):
                 )
 
 
-def _check_expression(expr):
+def _check_expression(expr) -> None:
     """
     Make sure an expression is not an empty string
 
@@ -144,7 +144,7 @@ def _convert_expression(expr) -> str:
     return s
 
 
-def _check_for_locals(expr: str, stack_level: int, parser: str):
+def _check_for_locals(expr: str, stack_level: int, parser: str) -> None:
 
     at_top_of_stack = stack_level == 0
     not_pandas_parser = parser != "pandas"
diff --git a/pandas/core/computation/expressions.py b/pandas/core/computation/expressions.py
index 9e180f11c4211..e82bec47c6ac5 100644
--- a/pandas/core/computation/expressions.py
+++ b/pandas/core/computation/expressions.py
@@ -38,7 +38,7 @@
 _MIN_ELEMENTS = 1_000_000
 
 
-def set_use_numexpr(v=True):
+def set_use_numexpr(v=True) -> None:
     # set/unset to use numexpr
     global USE_NUMEXPR
     if NUMEXPR_INSTALLED:
@@ -51,7 +51,7 @@ def set_use_numexpr(v=True):
     _where = _where_numexpr if USE_NUMEXPR else _where_standard
 
 
-def set_numexpr_threads(n=None):
+def set_numexpr_threads(n=None) -> None:
     # if we are using numexpr, set the threads to n
     # otherwise reset
     if NUMEXPR_INSTALLED and USE_NUMEXPR:
diff --git a/pandas/core/computation/ops.py b/pandas/core/computation/ops.py
index 3a556b57ea5a5..4215cc927ebf3 100644
--- a/pandas/core/computation/ops.py
+++ b/pandas/core/computation/ops.py
@@ -107,7 +107,7 @@ def _resolve_name(self):
             )
         return res
 
-    def update(self, value):
+    def update(self, value) -> None:
         """
         search order for local (i.e., @variable) variables:
 
@@ -162,7 +162,7 @@ def value(self):
         return self._value
 
     @value.setter
-    def value(self, new_value):
+    def value(self, new_value) -> None:
         self._value = new_value
 
     @property
@@ -321,7 +321,7 @@ def _not_in(x, y):
     _binary_ops_dict.update(d)
 
 
-def _cast_inplace(terms, acceptable_dtypes, dtype):
+def _cast_inplace(terms, acceptable_dtypes, dtype) -> None:
     """
     Cast an expression inplace.
 
@@ -480,7 +480,7 @@ def stringify(value):
                 v = v.tz_convert("UTC")
             self.lhs.update(v)
 
-    def _disallow_scalar_only_bool_ops(self):
+    def _disallow_scalar_only_bool_ops(self) -> None:
         rhs = self.rhs
         lhs = self.lhs
 
diff --git a/pandas/core/computation/pytables.py b/pandas/core/computation/pytables.py
index 29af322ba0b42..7601f607b7311 100644
--- a/pandas/core/computation/pytables.py
+++ b/pandas/core/computation/pytables.py
@@ -107,7 +107,7 @@ def __init__(self, op: str, lhs, rhs, queryables: dict[str, Any], encoding) -> N
         self.encoding = encoding
         self.condition = None
 
-    def _disallow_scalar_only_bool_ops(self):
+    def _disallow_scalar_only_bool_ops(self) -> None:
         pass
 
     def prune(self, klass):
@@ -256,7 +256,7 @@ def stringify(value):
         else:
             raise TypeError(f"Cannot compare {v} of type {type(v)} to {kind} column")
 
-    def convert_values(self):
+    def convert_values(self) -> None:
         pass
 
 
diff --git a/pandas/core/config_init.py b/pandas/core/config_init.py
index 47cf64ba24022..6413a09f30ffd 100644
--- a/pandas/core/config_init.py
+++ b/pandas/core/config_init.py
@@ -37,7 +37,7 @@
 """
 
 
-def use_bottleneck_cb(key):
+def use_bottleneck_cb(key) -> None:
     from pandas.core import nanops
 
     nanops.set_use_bottleneck(cf.get_option(key))
@@ -51,7 +51,7 @@ def use_bottleneck_cb(key):
 """
 
 
-def use_numexpr_cb(key):
+def use_numexpr_cb(key) -> None:
     from pandas.core.computation import expressions
 
     expressions.set_use_numexpr(cf.get_option(key))
@@ -65,7 +65,7 @@ def use_numexpr_cb(key):
 """
 
 
-def use_numba_cb(key):
+def use_numba_cb(key) -> None:
     from pandas.core.util import numba_
 
     numba_.set_use_numba(cf.get_option(key))
@@ -329,7 +329,7 @@ def use_numba_cb(key):
 """
 
 
-def table_schema_cb(key):
+def table_schema_cb(key) -> None:
     from pandas.io.formats.printing import enable_data_resource_formatter
 
     enable_data_resource_formatter(cf.get_option(key))
@@ -362,7 +362,7 @@ def is_terminal() -> bool:
         validator=is_one_of_factory([None, is_callable]),
     )
 
-    def _deprecate_column_space(key):
+    def _deprecate_column_space(key) -> None:
         warnings.warn(
             "column_space is deprecated and will be removed "
             "in a future version. Use df.to_string(col_space=...) "
@@ -387,7 +387,7 @@ def _deprecate_column_space(key):
     )
     cf.register_option("max_categories", 8, pc_max_categories_doc, validator=is_int)
 
-    def _deprecate_negative_int_max_colwidth(key):
+    def _deprecate_negative_int_max_colwidth(key) -> None:
         value = cf.get_option(key)
         if value is not None and value < 0:
             warnings.warn(
@@ -500,7 +500,7 @@ def _deprecate_negative_int_max_colwidth(key):
 # or we'll hit circular deps.
 
 
-def use_inf_as_na_cb(key):
+def use_inf_as_na_cb(key) -> None:
     from pandas.core.dtypes.missing import _use_inf_as_na
 
     _use_inf_as_na(key)
@@ -720,7 +720,7 @@ def use_inf_as_na_cb(key):
 """
 
 
-def register_plotting_backend_cb(key):
+def register_plotting_backend_cb(key) -> None:
     if key == "matplotlib":
         # We defer matplotlib validation, since it's the default
         return
@@ -746,7 +746,7 @@ def register_plotting_backend_cb(key):
 """
 
 
-def register_converter_cb(key):
+def register_converter_cb(key) -> None:
     from pandas.plotting import (
         deregister_matplotlib_converters,
         register_matplotlib_converters,
diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index d356a858a82fb..d0b7d10ce1dda 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -231,7 +231,7 @@ def _maybe_unbox_datetimelike(value: Scalar, dtype: DtypeObj) -> Scalar:
     return value
 
 
-def _disallow_mismatched_datetimelike(value, dtype: DtypeObj):
+def _disallow_mismatched_datetimelike(value, dtype: DtypeObj) -> None:
     """
     numpy allows np.array(dt64values, dtype="timedelta64[ns]") and
     vice-versa, but we do not want to allow this, so we need to
@@ -978,7 +978,7 @@ def maybe_upcast(
     return upcast_values, fill_value  # type: ignore[return-value]
 
 
-def invalidate_string_dtypes(dtype_set: set[DtypeObj]):
+def invalidate_string_dtypes(dtype_set: set[DtypeObj]) -> None:
     """
     Change string like dtypes to object for
     ``DataFrame.select_dtypes()``.
diff --git a/pandas/core/dtypes/dtypes.py b/pandas/core/dtypes/dtypes.py
index 32594854f49ae..348f6ef131864 100644
--- a/pandas/core/dtypes/dtypes.py
+++ b/pandas/core/dtypes/dtypes.py
@@ -970,7 +970,7 @@ def __eq__(self, other: Any) -> bool:
     def __ne__(self, other: Any) -> bool:
         return not self.__eq__(other)
 
-    def __setstate__(self, state):
+    def __setstate__(self, state) -> None:
         # for pickle compat. __getstate__ is defined in the
         # PandasExtensionDtype superclass and uses the public properties to
         # pickle -> need to set the settable private ones here (see GH26067)
@@ -1249,7 +1249,7 @@ def __eq__(self, other: Any) -> bool:
 
             return is_dtype_equal(self.subtype, other.subtype)
 
-    def __setstate__(self, state):
+    def __setstate__(self, state) -> None:
         # for pickle compat. __get_state__ is defined in the
         # PandasExtensionDtype superclass and uses the public properties to
         # pickle -> need to set the settable private ones here (see GH26067)
diff --git a/pandas/core/dtypes/missing.py b/pandas/core/dtypes/missing.py
index 37b42ad66c027..0def7faefa095 100644
--- a/pandas/core/dtypes/missing.py
+++ b/pandas/core/dtypes/missing.py
@@ -233,7 +233,7 @@ def _isna(obj, inf_as_na: bool = False):
         return False
 
 
-def _use_inf_as_na(key):
+def _use_inf_as_na(key) -> None:
     """
     Option change callback for na/inf behaviour.
 
diff --git a/pandas/core/flags.py b/pandas/core/flags.py
index 001cd3d41177a..cc779d98716c8 100644
--- a/pandas/core/flags.py
+++ b/pandas/core/flags.py
@@ -81,7 +81,7 @@ def allows_duplicate_labels(self) -> bool:
         return self._allows_duplicate_labels
 
     @allows_duplicate_labels.setter
-    def allows_duplicate_labels(self, value: bool):
+    def allows_duplicate_labels(self, value: bool) -> None:
         value = bool(value)
         obj = self._obj()
         if obj is None:
@@ -99,7 +99,7 @@ def __getitem__(self, key):
 
         return getattr(self, key)
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key, value) -> None:
         if key not in self._keys:
             raise ValueError(f"Unknown flag {key}. Must be one of {self._keys}")
         setattr(self, key, value)
diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index b4a278185b01b..5431a819fc825 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -3831,7 +3831,7 @@ def __setitem__(self, key, value):
             # set column
             self._set_item(key, value)
 
-    def _setitem_slice(self, key: slice, value):
+    def _setitem_slice(self, key: slice, value) -> None:
         # NB: we can't just use self.loc[key] = value because that
         #  operates on labels and we need to operate positional for
         #  backwards-compat, xref GH#31469
@@ -3923,7 +3923,7 @@ def igetitem(obj, i: int):
             finally:
                 self.columns = orig_columns
 
-    def _setitem_frame(self, key, value):
+    def _setitem_frame(self, key, value) -> None:
         # support boolean setting with DataFrame input, e.g.
         # df[df > df2] = 0
         if isinstance(key, np.ndarray):
diff --git a/pandas/core/generic.py b/pandas/core/generic.py
index 589ea6e67d926..53a6ce8f0aeea 100644
--- a/pandas/core/generic.py
+++ b/pandas/core/generic.py
@@ -2014,7 +2014,7 @@ def __getstate__(self) -> dict[str, Any]:
         }
 
     @final
-    def __setstate__(self, state):
+    def __setstate__(self, state) -> None:
         if isinstance(state, BlockManager):
             self._mgr = state
         elif isinstance(state, dict):
@@ -3887,7 +3887,7 @@ def _check_is_chained_assignment_possible(self) -> bool_t:
         return False
 
     @final
-    def _check_setitem_copy(self, t="setting", force=False):
+    def _check_setitem_copy(self, t="setting", force=False) -> None:
         """
 
         Parameters
@@ -3999,7 +3999,7 @@ def __delitem__(self, key) -> None:
     # Unsorted
 
     @final
-    def _check_inplace_and_allows_duplicate_labels(self, inplace):
+    def _check_inplace_and_allows_duplicate_labels(self, inplace) -> None:
         if inplace and not self.flags.allows_duplicate_labels:
             raise ValueError(
                 "Cannot specify 'inplace=True' when "
@@ -5679,7 +5679,7 @@ def _protect_consolidate(self, f):
     def _consolidate_inplace(self) -> None:
         """Consolidate data in place and return None"""
 
-        def f():
+        def f() -> None:
             self._mgr = self._mgr.consolidate()
 
         self._protect_consolidate(f)
diff --git a/pandas/core/groupby/grouper.py b/pandas/core/groupby/grouper.py
index 05ef155ecbcda..9e7c5e4d15a8c 100644
--- a/pandas/core/groupby/grouper.py
+++ b/pandas/core/groupby/grouper.py
@@ -942,7 +942,7 @@ def _convert_grouper(axis: Index, grouper):
         return grouper
 
 
-def _check_deprecated_resample_kwargs(kwargs, origin):
+def _check_deprecated_resample_kwargs(kwargs, origin) -> None:
     """
     Check for use of deprecated parameters in ``resample`` and related functions.
 
diff --git a/pandas/core/groupby/ops.py b/pandas/core/groupby/ops.py
index d056b4b03d904..410f046ff6767 100644
--- a/pandas/core/groupby/ops.py
+++ b/pandas/core/groupby/ops.py
@@ -222,7 +222,7 @@ def _get_cython_vals(self, values: np.ndarray) -> np.ndarray:
         return values
 
     # TODO: general case implementation overridable by EAs.
-    def _disallow_invalid_ops(self, dtype: DtypeObj, is_numeric: bool = False):
+    def _disallow_invalid_ops(self, dtype: DtypeObj, is_numeric: bool = False) -> None:
         """
         Check if we can do this operation with our cython functions.
 
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 0393c9d07cc74..8af5c1a381a69 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -661,7 +661,7 @@ def _dtype_to_subclass(cls, dtype: DtypeObj):
     """
 
     @property
-    def asi8(self):
+    def asi8(self) -> None:
         """
         Integer representation of the values.
 
@@ -1726,7 +1726,7 @@ def name(self):
         return self._name
 
     @name.setter
-    def name(self, value: Hashable):
+    def name(self, value: Hashable) -> None:
         if self._no_setting_name:
             # Used in MultiIndex.levels to avoid silently ignoring name updates.
             raise RuntimeError(
@@ -3192,7 +3192,7 @@ def _get_reconciled_name_object(self, other):
         return self
 
     @final
-    def _validate_sort_keyword(self, sort):
+    def _validate_sort_keyword(self, sort) -> None:
         if sort not in [None, False]:
             raise ValueError(
                 "The 'sort' keyword only takes the values of "
@@ -3200,7 +3200,7 @@ def _validate_sort_keyword(self, sort):
             )
 
     @final
-    def _deprecate_dti_setop(self, other: Index, setop: str_t):
+    def _deprecate_dti_setop(self, other: Index, setop: str_t) -> None:
         """
         Deprecate setop behavior between timezone-aware DatetimeIndexes with
         mismatched timezones.
@@ -5929,7 +5929,7 @@ def get_value(self, series: Series, key):
 
         return self._get_values_for_loc(series, loc, key)
 
-    def _check_indexing_error(self, key):
+    def _check_indexing_error(self, key) -> None:
         if not is_scalar(key):
             # if key is not a scalar, directly raise an error (the code below
             # would convert to numpy arrays and raise later any way) - GH29926
@@ -5957,7 +5957,7 @@ def _get_values_for_loc(self, series: Series, loc, key):
         return series.iloc[loc]
 
     @final
-    def set_value(self, arr, key, value):
+    def set_value(self, arr, key, value) -> None:
         """
         Fast lookup of value from 1-dimensional ndarray.
 
@@ -6590,7 +6590,7 @@ def _maybe_cast_listlike_indexer(self, target) -> Index:
         return ensure_index(target)
 
     @final
-    def _validate_indexer(self, form: str_t, key, kind: str_t):
+    def _validate_indexer(self, form: str_t, key, kind: str_t) -> None:
         """
         If we are positional indexer, validate that we have appropriate
         typed bounds must be an integer.
diff --git a/pandas/core/indexes/extension.py b/pandas/core/indexes/extension.py
index 28a0b43d5b02b..120c2b0eda11a 100644
--- a/pandas/core/indexes/extension.py
+++ b/pandas/core/indexes/extension.py
@@ -74,7 +74,7 @@ def fget(self):
                     return Index(result, name=self.name)
                 return result
 
-            def fset(self, value):
+            def fset(self, value) -> None:
                 setattr(self._data, name, value)
 
             fget.__name__ = name
diff --git a/pandas/core/indexes/multi.py b/pandas/core/indexes/multi.py
index 0a8df9d64d512..94f0f96bccb9f 100644
--- a/pandas/core/indexes/multi.py
+++ b/pandas/core/indexes/multi.py
@@ -1423,7 +1423,7 @@ def format(
     def _get_names(self) -> FrozenList:
         return FrozenList(self._names)
 
-    def _set_names(self, names, *, level=None, validate: bool = True):
+    def _set_names(self, names, *, level=None, validate: bool = True) -> None:
         """
         Set new names on index. Each name has to be a hashable type.
 
diff --git a/pandas/core/indexes/range.py b/pandas/core/indexes/range.py
index fdb1ee754a7e6..bc2b150bd3683 100644
--- a/pandas/core/indexes/range.py
+++ b/pandas/core/indexes/range.py
@@ -217,7 +217,7 @@ def _format_attrs(self):
             attrs.append(("name", ibase.default_pprint(self.name)))
         return attrs
 
-    def _format_data(self, name=None):
+    def _format_data(self, name=None) -> None:
         # we are formatting thru the attributes
         return None
 
diff --git a/pandas/core/indexing.py b/pandas/core/indexing.py
index 5a97e1d5a04ea..4d0e4bfc6fff4 100644
--- a/pandas/core/indexing.py
+++ b/pandas/core/indexing.py
@@ -754,7 +754,7 @@ def _maybe_mask_setitem_value(self, indexer, value):
         return indexer, value
 
     @final
-    def _ensure_listlike_indexer(self, key, axis=None, value=None):
+    def _ensure_listlike_indexer(self, key, axis=None, value=None) -> None:
         """
         Ensure that a list-like of column labels are all present by adding them if
         they do not already exist.
@@ -790,7 +790,7 @@ def _ensure_listlike_indexer(self, key, axis=None, value=None):
             self.obj._mgr = self.obj._mgr.reindex_axis(keys, axis=0, only_slice=True)
 
     @final
-    def __setitem__(self, key, value):
+    def __setitem__(self, key, value) -> None:
         check_deprecated_indexers(key)
         if isinstance(key, tuple):
             key = tuple(list(x) if is_iterator(x) else x for x in key)
@@ -1092,7 +1092,7 @@ class _LocIndexer(_LocationIndexer):
     # Key Checks
 
     @doc(_LocationIndexer._validate_key)
-    def _validate_key(self, key, axis: int):
+    def _validate_key(self, key, axis: int) -> None:
         # valid for a collection of labels (we check their presence later)
         # slice of labels (where start-end in labels)
         # slice of integers (only if in the labels)
@@ -1428,7 +1428,7 @@ class _iLocIndexer(_LocationIndexer):
     # -------------------------------------------------------------------
     # Key Checks
 
-    def _validate_key(self, key, axis: int):
+    def _validate_key(self, key, axis: int) -> None:
         if com.is_bool_indexer(key):
             if hasattr(key, "index") and isinstance(key.index, Index):
                 if key.index.inferred_type == "integer":
@@ -1638,7 +1638,7 @@ def _get_setitem_indexer(self, key):
 
     # -------------------------------------------------------------------
 
-    def _setitem_with_indexer(self, indexer, value, name="iloc"):
+    def _setitem_with_indexer(self, indexer, value, name="iloc") -> None:
         """
         _setitem_with_indexer is for setting values on a Series/DataFrame
         using positional indexers.
@@ -1868,7 +1868,7 @@ def _setitem_with_indexer_split_path(self, indexer, value, name: str):
             for loc in ilocs:
                 self._setitem_single_column(loc, value, pi)
 
-    def _setitem_with_indexer_2d_value(self, indexer, value):
+    def _setitem_with_indexer_2d_value(self, indexer, value) -> None:
         # We get here with np.ndim(value) == 2, excluding DataFrame,
         #  which goes through _setitem_with_indexer_frame_value
         pi = indexer[0]
@@ -1886,7 +1886,9 @@ def _setitem_with_indexer_2d_value(self, indexer, value):
             # setting with a list, re-coerces
             self._setitem_single_column(loc, value[:, i].tolist(), pi)
 
-    def _setitem_with_indexer_frame_value(self, indexer, value: DataFrame, name: str):
+    def _setitem_with_indexer_frame_value(
+        self, indexer, value: DataFrame, name: str
+    ) -> None:
         ilocs = self._ensure_iterable_column_indexer(indexer[1])
 
         sub_indexer = list(indexer)
@@ -1935,7 +1937,7 @@ def _setitem_with_indexer_frame_value(self, indexer, value: DataFrame, name: str
 
                 self._setitem_single_column(loc, val, pi)
 
-    def _setitem_single_column(self, loc: int, value, plane_indexer):
+    def _setitem_single_column(self, loc: int, value, plane_indexer) -> None:
         """
 
         Parameters
@@ -2009,7 +2011,7 @@ def _setitem_single_column(self, loc: int, value, plane_indexer):
                 # TODO: what if we got here indirectly via loc?
         return
 
-    def _setitem_single_block(self, indexer, value, name: str):
+    def _setitem_single_block(self, indexer, value, name: str) -> None:
         """
         _setitem_with_indexer for the case when we have a single Block.
         """
@@ -2335,7 +2337,7 @@ def __getitem__(self, key):
         key = self._convert_key(key)
         return self.obj._get_value(*key, takeable=self._takeable)
 
-    def __setitem__(self, key, value):
+    def __setitem__(self, key, value) -> None:
         if isinstance(key, tuple):
             key = tuple(com.apply_if_callable(x, self.obj) for x in key)
         else:
diff --git a/pandas/core/internals/array_manager.py b/pandas/core/internals/array_manager.py
index ee6c183898079..8463c5bc2bf65 100644
--- a/pandas/core/internals/array_manager.py
+++ b/pandas/core/internals/array_manager.py
@@ -176,7 +176,7 @@ def get_dtypes(self):
     def __getstate__(self):
         return self.arrays, self._axes
 
-    def __setstate__(self, state):
+    def __setstate__(self, state) -> None:
         self.arrays = state[0]
         self._axes = state[1]
 
@@ -812,7 +812,7 @@ def column_arrays(self) -> list[ArrayLike]:
 
     def iset(
         self, loc: int | slice | np.ndarray, value: ArrayLike, inplace: bool = False
-    ):
+    ) -> None:
         """
         Set new column(s).
 
@@ -1331,7 +1331,7 @@ def _get_data_subset(self, predicate: Callable) -> SingleArrayManager:
         else:
             return self.make_empty()
 
-    def set_values(self, values: ArrayLike):
+    def set_values(self, values: ArrayLike) -> None:
         """
         Set (replace) the values of the SingleArrayManager in place.
 
diff --git a/pandas/core/internals/blocks.py b/pandas/core/internals/blocks.py
index 49efecec7472e..7941835bc6a6a 100644
--- a/pandas/core/internals/blocks.py
+++ b/pandas/core/internals/blocks.py
@@ -215,7 +215,7 @@ def mgr_locs(self) -> BlockPlacement:
         return self._mgr_locs
 
     @mgr_locs.setter
-    def mgr_locs(self, new_mgr_locs: BlockPlacement):
+    def mgr_locs(self, new_mgr_locs: BlockPlacement) -> None:
         self._mgr_locs = new_mgr_locs
 
     @final
@@ -2156,7 +2156,7 @@ def new_block(values, placement, *, ndim: int) -> Block:
     return klass(values, ndim=ndim, placement=placement)
 
 
-def check_ndim(values, placement: BlockPlacement, ndim: int):
+def check_ndim(values, placement: BlockPlacement, ndim: int) -> None:
     """
     ndim inference and validation.
 
diff --git a/pandas/core/internals/concat.py b/pandas/core/internals/concat.py
index 4a352d614e1d9..e99a710941d19 100644
--- a/pandas/core/internals/concat.py
+++ b/pandas/core/internals/concat.py
@@ -359,7 +359,7 @@ def _get_mgr_concatenation_plan(mgr: BlockManager, indexers: dict[int, np.ndarra
 
 
 class JoinUnit:
-    def __init__(self, block: Block, shape: Shape, indexers=None):
+    def __init__(self, block: Block, shape: Shape, indexers=None) -> None:
         # Passing shape explicitly is required for cases when block is None.
         # Note: block is None implies indexers is None, but not vice-versa
         if indexers is None:
diff --git a/pandas/core/internals/managers.py b/pandas/core/internals/managers.py
index 7cccc9833de6b..c4bd3453e0a9a 100644
--- a/pandas/core/internals/managers.py
+++ b/pandas/core/internals/managers.py
@@ -1773,7 +1773,7 @@ def unpickle_block(values, mgr_locs, ndim: int) -> Block:
 
         self._post_setstate()
 
-    def _post_setstate(self):
+    def _post_setstate(self) -> None:
         pass
 
     @cache_readonly
@@ -1781,12 +1781,12 @@ def _block(self) -> Block:
         return self.blocks[0]
 
     @property
-    def _blknos(self):
+    def _blknos(self) -> None:
         """compat with BlockManager"""
         return None
 
     @property
-    def _blklocs(self):
+    def _blklocs(self) -> None:
         """compat with BlockManager"""
         return None
 
@@ -1870,7 +1870,7 @@ def fast_xs(self, loc):
         """
         raise NotImplementedError("Use series._values[loc] instead")
 
-    def set_values(self, values: ArrayLike):
+    def set_values(self, values: ArrayLike) -> None:
         """
         Set the values of the single block in place.
 
diff --git a/pandas/core/internals/ops.py b/pandas/core/internals/ops.py
index 1160d3b2a8e3a..24fc51a96d9df 100644
--- a/pandas/core/internals/ops.py
+++ b/pandas/core/internals/ops.py
@@ -86,7 +86,7 @@ def operate_blockwise(
     return new_mgr
 
 
-def _reset_block_mgr_locs(nbs: list[Block], locs):
+def _reset_block_mgr_locs(nbs: list[Block], locs) -> None:
     """
     Reset mgr_locs to correspond to our original DataFrame.
     """
diff --git a/pandas/core/missing.py b/pandas/core/missing.py
index 57b0a95f803b1..9eac047f003d0 100644
--- a/pandas/core/missing.py
+++ b/pandas/core/missing.py
@@ -376,7 +376,7 @@ def _interpolate_1d(
     bounds_error: bool = False,
     order: int | None = None,
     **kwargs,
-):
+) -> None:
     """
     Logic for the 1-d interpolation.  The input
     indices and yvalues will each be 1-d arrays of the same length.
diff --git a/pandas/core/ops/array_ops.py b/pandas/core/ops/array_ops.py
index 2caaadbc05cff..d90a9a42e6454 100644
--- a/pandas/core/ops/array_ops.py
+++ b/pandas/core/ops/array_ops.py
@@ -509,7 +509,7 @@ def maybe_prepare_scalar_for_op(obj, shape: Shape):
 }
 
 
-def _bool_arith_check(op, a, b):
+def _bool_arith_check(op, a, b) -> None:
     """
     In contrast to numpy, pandas raises an error for certain operations
     with booleans.
diff --git a/pandas/core/ops/invalid.py b/pandas/core/ops/invalid.py
index cc4a1f11edd2b..4d9cf3ceac4de 100644
--- a/pandas/core/ops/invalid.py
+++ b/pandas/core/ops/invalid.py
@@ -48,7 +48,7 @@ def make_invalid_op(name: str):
     invalid_op : function
     """
 
-    def invalid_op(self, other=None):
+    def invalid_op(self, other=None) -> None:
         typ = type(self).__name__
         raise TypeError(f"cannot perform {name} with this index type: {typ}")
 
diff --git a/pandas/core/ops/mask_ops.py b/pandas/core/ops/mask_ops.py
index 57bacba0d4bee..adc1f63c568bf 100644
--- a/pandas/core/ops/mask_ops.py
+++ b/pandas/core/ops/mask_ops.py
@@ -184,6 +184,6 @@ def kleene_and(
     return result, mask
 
 
-def raise_for_nan(value, method: str):
+def raise_for_nan(value, method: str) -> None:
     if lib.is_float(value) and np.isnan(value):
         raise ValueError(f"Cannot perform logical '{method}' with floating NaN")
diff --git a/pandas/core/ops/methods.py b/pandas/core/ops/methods.py
index df22919ed19f1..cfb1649c14734 100644
--- a/pandas/core/ops/methods.py
+++ b/pandas/core/ops/methods.py
@@ -43,7 +43,7 @@ def _get_method_wrappers(cls):
     return arith_flex, comp_flex
 
 
-def add_flex_arithmetic_methods(cls):
+def add_flex_arithmetic_methods(cls) -> None:
     """
     Adds the full suite of flex arithmetic methods (``pow``, ``mul``, ``add``)
     to the class.
@@ -117,6 +117,6 @@ def _create_methods(cls, arith_method, comp_method):
     return new_methods
 
 
-def _add_methods(cls, new_methods):
+def _add_methods(cls, new_methods) -> None:
     for name, method in new_methods.items():
         setattr(cls, name, method)
diff --git a/pandas/core/reshape/concat.py b/pandas/core/reshape/concat.py
index 523cd56db3e0a..a7cd0479b4d32 100644
--- a/pandas/core/reshape/concat.py
+++ b/pandas/core/reshape/concat.py
@@ -697,7 +697,7 @@ def _get_concat_axis(self) -> Index:
 
         return concat_axis
 
-    def _maybe_check_integrity(self, concat_index: Index):
+    def _maybe_check_integrity(self, concat_index: Index) -> None:
         if self.verify_integrity:
             if not concat_index.is_unique:
                 overlap = concat_index[concat_index.duplicated()].unique()
diff --git a/pandas/core/reshape/encoding.py b/pandas/core/reshape/encoding.py
index f0500ec142955..c0a43d4766fa0 100644
--- a/pandas/core/reshape/encoding.py
+++ b/pandas/core/reshape/encoding.py
@@ -143,7 +143,7 @@ def get_dummies(
             data_to_encode = data[columns]
 
         # validate prefixes and separator to avoid silently dropping cols
-        def check_len(item, name):
+        def check_len(item, name) -> None:
 
             if is_list_like(item):
                 if not len(item) == data_to_encode.shape[1]:
diff --git a/pandas/core/reshape/reshape.py b/pandas/core/reshape/reshape.py
index b4e944861f1bc..e083de96f892f 100644
--- a/pandas/core/reshape/reshape.py
+++ b/pandas/core/reshape/reshape.py
@@ -162,7 +162,7 @@ def _make_sorted_values(self, values: np.ndarray) -> np.ndarray:
         sorted_values = algos.take_nd(values, indexer, axis=0)
         return sorted_values
 
-    def _make_selectors(self):
+    def _make_selectors(self) -> None:
         new_levels = self.new_index_levels
 
         # make the mask
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 6ebee74810305..7e8e19c40c9ae 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -1165,7 +1165,7 @@ def _set_with_engine(self, key, value) -> None:
         # this is equivalent to self._values[key] = value
         self._mgr.setitem_inplace(loc, value)
 
-    def _set_with(self, key, value):
+    def _set_with(self, key, value) -> None:
         # We got here via exception-handling off of InvalidIndexError, so
         #  key should always be listlike at this point.
         assert not isinstance(key, tuple)
@@ -1203,7 +1203,7 @@ def _set_values(self, key, value) -> None:
         self._mgr = self._mgr.setitem(indexer=key, value=value)
         self._maybe_update_cacher()
 
-    def _set_value(self, label, value, takeable: bool = False):
+    def _set_value(self, label, value, takeable: bool = False) -> None:
         """
         Quickly set single value at passed label.
 
diff --git a/pandas/core/window/ewm.py b/pandas/core/window/ewm.py
index a153761f377b3..e955e4e228476 100644
--- a/pandas/core/window/ewm.py
+++ b/pandas/core/window/ewm.py
@@ -948,7 +948,7 @@ def __init__(
         else:
             raise ValueError("'numba' is the only supported engine")
 
-    def reset(self):
+    def reset(self) -> None:
         """
         Reset the state captured by `update` calls.
         """
diff --git a/pandas/core/window/online.py b/pandas/core/window/online.py
index 2ef06732f9800..bb973f05687e2 100644
--- a/pandas/core/window/online.py
+++ b/pandas/core/window/online.py
@@ -112,6 +112,6 @@ def run_ewm(self, weighted_avg, deltas, min_periods, ewm_func):
         self.last_ewm = result[-1]
         return result
 
-    def reset(self):
+    def reset(self) -> None:
         self.old_wt = np.ones(self.shape[self.axis - 1])
         self.last_ewm = None
diff --git a/pandas/core/window/rolling.py b/pandas/core/window/rolling.py
index b45f43adbe952..45170c26fb148 100644
--- a/pandas/core/window/rolling.py
+++ b/pandas/core/window/rolling.py
@@ -1154,7 +1154,7 @@ class Window(BaseWindow):
         "method",
     ]
 
-    def _validate(self):
+    def _validate(self) -> None:
         super()._validate()
 
         if not isinstance(self.win_type, str):
@@ -1817,7 +1817,7 @@ class Rolling(RollingAndExpandingMixin):
         "method",
     ]
 
-    def _validate(self):
+    def _validate(self) -> None:
         super()._validate()
 
         # we allow rolling on a datetimelike index
@@ -1862,7 +1862,7 @@ def _validate(self):
         elif not is_integer(self.window) or self.window < 0:
             raise ValueError("window must be an integer 0 or greater")
 
-    def _validate_datetimelike_monotonic(self):
+    def _validate_datetimelike_monotonic(self) -> None:
         """
         Validate self._on is monotonic (increasing or decreasing) and has
         no NaT values for frequency windows.
@@ -1872,7 +1872,7 @@ def _validate_datetimelike_monotonic(self):
         if not (self._on.is_monotonic_increasing or self._on.is_monotonic_decreasing):
             self._raise_monotonic_error("values must be monotonic")
 
-    def _raise_monotonic_error(self, msg: str):
+    def _raise_monotonic_error(self, msg: str) -> None:
         on = self.on
         if on is None:
             if self.axis == 0:
@@ -2865,7 +2865,7 @@ def _get_window_indexer(self) -> GroupbyIndexer:
         )
         return window_indexer
 
-    def _validate_datetimelike_monotonic(self):
+    def _validate_datetimelike_monotonic(self) -> None:
         """
         Validate that each group in self._on is monotonic
         """

From 91308daf5643256bfe8cc3b36a8bf9bbe0a8ab59 Mon Sep 17 00:00:00 2001
From: Marco Gorelli <marcogorelli@protonmail.com>
Date: Mon, 27 Jun 2022 19:47:01 +0200
Subject: [PATCH 2/2] type return of Index.asi8 to be compatible with
 overridden method

---
 pandas/core/indexes/base.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 8af5c1a381a69..f05c216bf6494 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -661,7 +661,7 @@ def _dtype_to_subclass(cls, dtype: DtypeObj):
     """
 
     @property
-    def asi8(self) -> None:
+    def asi8(self) -> npt.NDArray[np.int64] | None:
         """
         Integer representation of the values.