diff --git a/pandas/__init__.py b/pandas/__init__.py
index 1c4151372273b..01ff2e1e1f181 100644
--- a/pandas/__init__.py
+++ b/pandas/__init__.py
@@ -1,4 +1,5 @@
 # flake8: noqa
+from __future__ import annotations
 
 __docformat__ = "restructuredtext"
 
@@ -185,7 +186,7 @@
 __deprecated_num_index_names = ["Float64Index", "Int64Index", "UInt64Index"]
 
 
-def __dir__():
+def __dir__() -> list[str]:
     # GH43028
     # Int64Index etc. are deprecated, but we still want them to be available in the dir.
     # Remove in Pandas 2.0, when we remove Int64Index etc. from the code base.
diff --git a/pandas/_config/config.py b/pandas/_config/config.py
index 756c3b2d4b2b6..eacbf1b016432 100644
--- a/pandas/_config/config.py
+++ b/pandas/_config/config.py
@@ -60,6 +60,7 @@
     Callable,
     Generic,
     Iterable,
+    Iterator,
     NamedTuple,
     cast,
 )
@@ -435,13 +436,13 @@ def __init__(self, *args) -> None:
 
         self.ops = list(zip(args[::2], args[1::2]))
 
-    def __enter__(self):
+    def __enter__(self) -> None:
         self.undo = [(pat, _get_option(pat, silent=True)) for pat, val in self.ops]
 
         for pat, val in self.ops:
             _set_option(pat, val, silent=True)
 
-    def __exit__(self, *args):
+    def __exit__(self, *args) -> None:
         if self.undo:
             for pat, val in self.undo:
                 _set_option(pat, val, silent=True)
@@ -733,7 +734,7 @@ def pp(name: str, ks: Iterable[str]) -> list[str]:
 
 
 @contextmanager
-def config_prefix(prefix):
+def config_prefix(prefix) -> Iterator[None]:
     """
     contextmanager for multiple invocations of API with a common prefix
 
diff --git a/pandas/_testing/__init__.py b/pandas/_testing/__init__.py
index 9d3e84dc964d6..0fcea111716ec 100644
--- a/pandas/_testing/__init__.py
+++ b/pandas/_testing/__init__.py
@@ -238,7 +238,7 @@
 _testing_mode_warnings = (DeprecationWarning, ResourceWarning)
 
 
-def set_testing_mode():
+def set_testing_mode() -> None:
     # set the testing mode filters
     testing_mode = os.environ.get("PANDAS_TESTING_MODE", "None")
     if "deprecate" in testing_mode:
@@ -246,7 +246,7 @@ def set_testing_mode():
             warnings.simplefilter("always", category)
 
 
-def reset_testing_mode():
+def reset_testing_mode() -> None:
     # reset the testing mode filters
     testing_mode = os.environ.get("PANDAS_TESTING_MODE", "None")
     if "deprecate" in testing_mode:
@@ -257,7 +257,7 @@ def reset_testing_mode():
 set_testing_mode()
 
 
-def reset_display_options():
+def reset_display_options() -> None:
     """
     Reset the display options for printing and representing objects.
     """
@@ -333,16 +333,16 @@ def to_array(obj):
 # Others
 
 
-def getCols(k):
+def getCols(k) -> str:
     return string.ascii_uppercase[:k]
 
 
 # make index
-def makeStringIndex(k=10, name=None):
+def makeStringIndex(k=10, name=None) -> Index:
     return Index(rands_array(nchars=10, size=k), name=name)
 
 
-def makeCategoricalIndex(k=10, n=3, name=None, **kwargs):
+def makeCategoricalIndex(k=10, n=3, name=None, **kwargs) -> CategoricalIndex:
     """make a length k index or n categories"""
     x = rands_array(nchars=4, size=n, replace=False)
     return CategoricalIndex(
@@ -350,13 +350,13 @@ def makeCategoricalIndex(k=10, n=3, name=None, **kwargs):
     )
 
 
-def makeIntervalIndex(k=10, name=None, **kwargs):
+def makeIntervalIndex(k=10, name=None, **kwargs) -> IntervalIndex:
     """make a length k IntervalIndex"""
     x = np.linspace(0, 100, num=(k + 1))
     return IntervalIndex.from_breaks(x, name=name, **kwargs)
 
 
-def makeBoolIndex(k=10, name=None):
+def makeBoolIndex(k=10, name=None) -> Index:
     if k == 1:
         return Index([True], name=name)
     elif k == 2:
@@ -364,7 +364,7 @@ def makeBoolIndex(k=10, name=None):
     return Index([False, True] + [False] * (k - 2), name=name)
 
 
-def makeNumericIndex(k=10, name=None, *, dtype):
+def makeNumericIndex(k=10, name=None, *, dtype) -> NumericIndex:
     dtype = pandas_dtype(dtype)
     assert isinstance(dtype, np.dtype)
 
@@ -382,21 +382,21 @@ def makeNumericIndex(k=10, name=None, *, dtype):
     return NumericIndex(values, dtype=dtype, name=name)
 
 
-def makeIntIndex(k=10, name=None):
+def makeIntIndex(k=10, name=None) -> Int64Index:
     base_idx = makeNumericIndex(k, name=name, dtype="int64")
     return Int64Index(base_idx)
 
 
-def makeUIntIndex(k=10, name=None):
+def makeUIntIndex(k=10, name=None) -> UInt64Index:
     base_idx = makeNumericIndex(k, name=name, dtype="uint64")
     return UInt64Index(base_idx)
 
 
-def makeRangeIndex(k=10, name=None, **kwargs):
+def makeRangeIndex(k=10, name=None, **kwargs) -> RangeIndex:
     return RangeIndex(0, k, 1, name=name, **kwargs)
 
 
-def makeFloatIndex(k=10, name=None):
+def makeFloatIndex(k=10, name=None) -> Float64Index:
     base_idx = makeNumericIndex(k, name=name, dtype="float64")
     return Float64Index(base_idx)
 
@@ -456,34 +456,34 @@ def all_timeseries_index_generator(k: int = 10) -> Iterable[Index]:
 
 
 # make series
-def make_rand_series(name=None, dtype=np.float64):
+def make_rand_series(name=None, dtype=np.float64) -> Series:
     index = makeStringIndex(_N)
     data = np.random.randn(_N)
     data = data.astype(dtype, copy=False)
     return Series(data, index=index, name=name)
 
 
-def makeFloatSeries(name=None):
+def makeFloatSeries(name=None) -> Series:
     return make_rand_series(name=name)
 
 
-def makeStringSeries(name=None):
+def makeStringSeries(name=None) -> Series:
     return make_rand_series(name=name)
 
 
-def makeObjectSeries(name=None):
+def makeObjectSeries(name=None) -> Series:
     data = makeStringIndex(_N)
     data = Index(data, dtype=object)
     index = makeStringIndex(_N)
     return Series(data, index=index, name=name)
 
 
-def getSeriesData():
+def getSeriesData() -> dict[str, Series]:
     index = makeStringIndex(_N)
     return {c: Series(np.random.randn(_N), index=index) for c in getCols(_K)}
 
 
-def makeTimeSeries(nper=None, freq="B", name=None):
+def makeTimeSeries(nper=None, freq="B", name=None) -> Series:
     if nper is None:
         nper = _N
     return Series(
@@ -491,22 +491,22 @@ def makeTimeSeries(nper=None, freq="B", name=None):
     )
 
 
-def makePeriodSeries(nper=None, name=None):
+def makePeriodSeries(nper=None, name=None) -> Series:
     if nper is None:
         nper = _N
     return Series(np.random.randn(nper), index=makePeriodIndex(nper), name=name)
 
 
-def getTimeSeriesData(nper=None, freq="B"):
+def getTimeSeriesData(nper=None, freq="B") -> dict[str, Series]:
     return {c: makeTimeSeries(nper, freq) for c in getCols(_K)}
 
 
-def getPeriodData(nper=None):
+def getPeriodData(nper=None) -> dict[str, Series]:
     return {c: makePeriodSeries(nper) for c in getCols(_K)}
 
 
 # make frame
-def makeTimeDataFrame(nper=None, freq="B"):
+def makeTimeDataFrame(nper=None, freq="B") -> DataFrame:
     data = getTimeSeriesData(nper, freq)
     return DataFrame(data)
 
@@ -533,14 +533,19 @@ def makeMixedDataFrame():
     return DataFrame(getMixedTypeDict()[1])
 
 
-def makePeriodFrame(nper=None):
+def makePeriodFrame(nper=None) -> DataFrame:
     data = getPeriodData(nper)
     return DataFrame(data)
 
 
 def makeCustomIndex(
-    nentries, nlevels, prefix="#", names=False, ndupe_l=None, idx_type=None
-):
+    nentries,
+    nlevels,
+    prefix="#",
+    names: bool | str | list[str] | None = False,
+    ndupe_l=None,
+    idx_type=None,
+) -> Index:
     """
     Create an index/multindex with given dimensions, levels, names, etc'
 
@@ -637,7 +642,8 @@ def keyfunc(x):
     # convert tuples to index
     if nentries == 1:
         # we have a single level of tuples, i.e. a regular Index
-        index = Index(tuples[0], name=names[0])
+        name = None if names is None else names[0]
+        index = Index(tuples[0], name=name)
     elif nlevels == 1:
         name = None if names is None else names[0]
         index = Index((x[0] for x in tuples), name=name)
@@ -659,7 +665,7 @@ def makeCustomDataframe(
     dtype=None,
     c_idx_type=None,
     r_idx_type=None,
-):
+) -> DataFrame:
     """
     Create a DataFrame using supplied parameters.
 
@@ -780,7 +786,7 @@ def _gen_unique_rand(rng, _extra_size):
     return i.tolist(), j.tolist()
 
 
-def makeMissingDataframe(density=0.9, random_state=None):
+def makeMissingDataframe(density=0.9, random_state=None) -> DataFrame:
     df = makeDataFrame()
     i, j = _create_missing_idx(*df.shape, density=density, random_state=random_state)
     df.values[i, j] = np.nan
@@ -854,7 +860,7 @@ def skipna_wrapper(x):
     return skipna_wrapper
 
 
-def convert_rows_list_to_csv_str(rows_list: list[str]):
+def convert_rows_list_to_csv_str(rows_list: list[str]) -> str:
     """
     Convert list of CSV rows to single CSV-formatted string for current OS.
 
diff --git a/pandas/_testing/_io.py b/pandas/_testing/_io.py
index 46f1545a67fab..d1acdff8d2fd7 100644
--- a/pandas/_testing/_io.py
+++ b/pandas/_testing/_io.py
@@ -250,7 +250,7 @@ def wrapper(*args, **kwargs):
     return wrapper
 
 
-def can_connect(url, error_classes=None):
+def can_connect(url, error_classes=None) -> bool:
     """
     Try to connect to the given url. True if succeeds, False if OSError
     raised
@@ -424,7 +424,7 @@ def write_to_compressed(compression, path, data, dest="test"):
 # Plotting
 
 
-def close(fignum=None):
+def close(fignum=None) -> None:
     from matplotlib.pyplot import (
         close as _close,
         get_fignums,
diff --git a/pandas/_testing/_random.py b/pandas/_testing/_random.py
index cce6bf8da7d3e..880fffea21bd1 100644
--- a/pandas/_testing/_random.py
+++ b/pandas/_testing/_random.py
@@ -14,7 +14,7 @@ def randbool(size=(), p: float = 0.5):
 )
 
 
-def rands_array(nchars, size, dtype="O", replace=True):
+def rands_array(nchars, size, dtype="O", replace=True) -> np.ndarray:
     """
     Generate an array of byte strings.
     """
@@ -26,7 +26,7 @@ def rands_array(nchars, size, dtype="O", replace=True):
     return retval.astype(dtype)
 
 
-def rands(nchars):
+def rands(nchars) -> str:
     """
     Generate one random byte string.
 
diff --git a/pandas/_testing/asserters.py b/pandas/_testing/asserters.py
index 90ee600c1967d..5e8b553b352c8 100644
--- a/pandas/_testing/asserters.py
+++ b/pandas/_testing/asserters.py
@@ -68,7 +68,7 @@ def assert_almost_equal(
     rtol: float = 1.0e-5,
     atol: float = 1.0e-8,
     **kwargs,
-):
+) -> None:
     """
     Check that the left and right objects are approximately equal.
 
@@ -239,7 +239,7 @@ def _check_isinstance(left, right, cls):
         )
 
 
-def assert_dict_equal(left, right, compare_keys: bool = True):
+def assert_dict_equal(left, right, compare_keys: bool = True) -> None:
 
     _check_isinstance(left, right, dict)
     _testing.assert_dict_equal(left, right, compare_keys=compare_keys)
@@ -428,7 +428,7 @@ def _get_ilevel_values(index, level):
             assert_categorical_equal(left._values, right._values, obj=f"{obj} category")
 
 
-def assert_class_equal(left, right, exact: bool | str = True, obj="Input"):
+def assert_class_equal(left, right, exact: bool | str = True, obj="Input") -> None:
     """
     Checks classes are equal.
     """
@@ -455,7 +455,7 @@ def repr_class(x):
     raise_assert_detail(obj, msg, repr_class(left), repr_class(right))
 
 
-def assert_attr_equal(attr: str, left, right, obj: str = "Attributes"):
+def assert_attr_equal(attr: str, left, right, obj: str = "Attributes") -> None:
     """
     Check attributes are equal. Both objects must have attribute.
 
@@ -474,11 +474,9 @@ def assert_attr_equal(attr: str, left, right, obj: str = "Attributes"):
     left_attr = getattr(left, attr)
     right_attr = getattr(right, attr)
 
-    if left_attr is right_attr:
-        return True
-    elif is_matching_na(left_attr, right_attr):
+    if left_attr is right_attr or is_matching_na(left_attr, right_attr):
         # e.g. both np.nan, both NaT, both pd.NA, ...
-        return True
+        return None
 
     try:
         result = left_attr == right_attr
@@ -490,14 +488,13 @@ def assert_attr_equal(attr: str, left, right, obj: str = "Attributes"):
     elif not isinstance(result, bool):
         result = result.all()
 
-    if result:
-        return True
-    else:
+    if not result:
         msg = f'Attribute "{attr}" are different'
         raise_assert_detail(obj, msg, left_attr, right_attr)
+    return None
 
 
-def assert_is_valid_plot_return_object(objs):
+def assert_is_valid_plot_return_object(objs) -> None:
     import matplotlib.pyplot as plt
 
     if isinstance(objs, (Series, np.ndarray)):
@@ -516,7 +513,7 @@ def assert_is_valid_plot_return_object(objs):
         assert isinstance(objs, (plt.Artist, tuple, dict)), msg
 
 
-def assert_is_sorted(seq):
+def assert_is_sorted(seq) -> None:
     """Assert that the sequence is sorted."""
     if isinstance(seq, (Index, Series)):
         seq = seq.values
@@ -526,7 +523,7 @@ def assert_is_sorted(seq):
 
 def assert_categorical_equal(
     left, right, check_dtype=True, check_category_order=True, obj="Categorical"
-):
+) -> None:
     """
     Test that Categoricals are equivalent.
 
@@ -581,7 +578,9 @@ def assert_categorical_equal(
     assert_attr_equal("ordered", left, right, obj=obj)
 
 
-def assert_interval_array_equal(left, right, exact="equiv", obj="IntervalArray"):
+def assert_interval_array_equal(
+    left, right, exact="equiv", obj="IntervalArray"
+) -> None:
     """
     Test that two IntervalArrays are equivalent.
 
@@ -610,14 +609,16 @@ def assert_interval_array_equal(left, right, exact="equiv", obj="IntervalArray")
     assert_attr_equal("inclusive", left, right, obj=obj)
 
 
-def assert_period_array_equal(left, right, obj="PeriodArray"):
+def assert_period_array_equal(left, right, obj="PeriodArray") -> None:
     _check_isinstance(left, right, PeriodArray)
 
     assert_numpy_array_equal(left._data, right._data, obj=f"{obj}._data")
     assert_attr_equal("freq", left, right, obj=obj)
 
 
-def assert_datetime_array_equal(left, right, obj="DatetimeArray", check_freq=True):
+def assert_datetime_array_equal(
+    left, right, obj="DatetimeArray", check_freq=True
+) -> None:
     __tracebackhide__ = True
     _check_isinstance(left, right, DatetimeArray)
 
@@ -627,7 +628,9 @@ def assert_datetime_array_equal(left, right, obj="DatetimeArray", check_freq=Tru
     assert_attr_equal("tz", left, right, obj=obj)
 
 
-def assert_timedelta_array_equal(left, right, obj="TimedeltaArray", check_freq=True):
+def assert_timedelta_array_equal(
+    left, right, obj="TimedeltaArray", check_freq=True
+) -> None:
     __tracebackhide__ = True
     _check_isinstance(left, right, TimedeltaArray)
     assert_numpy_array_equal(left._data, right._data, obj=f"{obj}._data")
@@ -682,7 +685,7 @@ def assert_numpy_array_equal(
     check_same=None,
     obj="numpy array",
     index_values=None,
-):
+) -> None:
     """
     Check that 'np.ndarray' is equivalent.
 
@@ -762,7 +765,7 @@ def assert_extension_array_equal(
     check_exact=False,
     rtol: float = 1.0e-5,
     atol: float = 1.0e-8,
-):
+) -> None:
     """
     Check that left and right ExtensionArrays are equal.
 
@@ -878,7 +881,7 @@ def assert_series_equal(
     *,
     check_index=True,
     check_like=False,
-):
+) -> None:
     """
     Check that left and right Series are equal.
 
@@ -1145,7 +1148,7 @@ def assert_frame_equal(
     rtol=1.0e-5,
     atol=1.0e-8,
     obj="DataFrame",
-):
+) -> None:
     """
     Check that left and right DataFrame are equal.
 
@@ -1352,7 +1355,7 @@ def assert_frame_equal(
             )
 
 
-def assert_equal(left, right, **kwargs):
+def assert_equal(left, right, **kwargs) -> None:
     """
     Wrapper for tm.assert_*_equal to dispatch to the appropriate test function.
 
@@ -1393,7 +1396,7 @@ def assert_equal(left, right, **kwargs):
         assert_almost_equal(left, right)
 
 
-def assert_sp_array_equal(left, right):
+def assert_sp_array_equal(left, right) -> None:
     """
     Check that the left and right SparseArray are equal.
 
@@ -1426,12 +1429,12 @@ def assert_sp_array_equal(left, right):
     assert_numpy_array_equal(left.to_dense(), right.to_dense())
 
 
-def assert_contains_all(iterable, dic):
+def assert_contains_all(iterable, dic) -> None:
     for k in iterable:
         assert k in dic, f"Did not contain item: {repr(k)}"
 
 
-def assert_copy(iter1, iter2, **eql_kwargs):
+def assert_copy(iter1, iter2, **eql_kwargs) -> None:
     """
     iter1, iter2: iterables that produce elements
     comparable with assert_almost_equal
@@ -1463,7 +1466,7 @@ def is_extension_array_dtype_and_needs_i8_conversion(left_dtype, right_dtype) ->
     return is_extension_array_dtype(left_dtype) and needs_i8_conversion(right_dtype)
 
 
-def assert_indexing_slices_equivalent(ser: Series, l_slc: slice, i_slc: slice):
+def assert_indexing_slices_equivalent(ser: Series, l_slc: slice, i_slc: slice) -> None:
     """
     Check that ser.iloc[i_slc] matches ser.loc[l_slc] and, if applicable,
     ser[l_slc].
@@ -1477,7 +1480,7 @@ def assert_indexing_slices_equivalent(ser: Series, l_slc: slice, i_slc: slice):
         assert_series_equal(ser[l_slc], expected)
 
 
-def assert_metadata_equivalent(left, right):
+def assert_metadata_equivalent(left, right) -> None:
     """
     Check that ._metadata attributes are equivalent.
     """
diff --git a/pandas/_testing/contexts.py b/pandas/_testing/contexts.py
index 7df9afd68b432..e64adb06bea7a 100644
--- a/pandas/_testing/contexts.py
+++ b/pandas/_testing/contexts.py
@@ -8,6 +8,7 @@
 from typing import (
     IO,
     Any,
+    Iterator,
 )
 import uuid
 
@@ -19,7 +20,7 @@
 
 
 @contextmanager
-def decompress_file(path, compression):
+def decompress_file(path, compression) -> Iterator[IO[bytes]]:
     """
     Open a compressed file and return a file object.
 
@@ -40,7 +41,7 @@ def decompress_file(path, compression):
 
 
 @contextmanager
-def set_timezone(tz: str):
+def set_timezone(tz: str) -> Iterator[None]:
     """
     Context manager for temporarily setting a timezone.
 
@@ -126,7 +127,7 @@ def ensure_clean(filename=None, return_filelike: bool = False, **kwargs: Any):
 
 
 @contextmanager
-def ensure_clean_dir():
+def ensure_clean_dir() -> Iterator[str]:
     """
     Get a temporary directory path and agrees to remove on close.
 
@@ -145,7 +146,7 @@ def ensure_clean_dir():
 
 
 @contextmanager
-def ensure_safe_environment_variables():
+def ensure_safe_environment_variables() -> Iterator[None]:
     """
     Get a context manager to safely set environment variables
 
@@ -161,7 +162,7 @@ def ensure_safe_environment_variables():
 
 
 @contextmanager
-def with_csv_dialect(name, **kwargs):
+def with_csv_dialect(name, **kwargs) -> Iterator[None]:
     """
     Context manager to temporarily register a CSV dialect for parsing CSV.
 
@@ -195,7 +196,7 @@ def with_csv_dialect(name, **kwargs):
 
 
 @contextmanager
-def use_numexpr(use, min_elements=None):
+def use_numexpr(use, min_elements=None) -> Iterator[None]:
     from pandas.core.computation import expressions as expr
 
     if min_elements is None:
@@ -231,11 +232,11 @@ class RNGContext:
     def __init__(self, seed) -> None:
         self.seed = seed
 
-    def __enter__(self):
+    def __enter__(self) -> None:
 
         self.start_state = np.random.get_state()
         np.random.seed(self.seed)
 
-    def __exit__(self, exc_type, exc_value, traceback):
+    def __exit__(self, exc_type, exc_value, traceback) -> None:
 
         np.random.set_state(self.start_state)
diff --git a/pandas/compat/__init__.py b/pandas/compat/__init__.py
index bb4787f07b2f0..2ab710a5762d3 100644
--- a/pandas/compat/__init__.py
+++ b/pandas/compat/__init__.py
@@ -7,9 +7,12 @@
 Other items:
 * platform checker
 """
+from __future__ import annotations
+
 import os
 import platform
 import sys
+from typing import TYPE_CHECKING
 
 from pandas._typing import F
 from pandas.compat.numpy import (
@@ -26,6 +29,9 @@
     pa_version_under7p0,
 )
 
+if TYPE_CHECKING:
+    import lzma
+
 PY39 = sys.version_info >= (3, 9)
 PY310 = sys.version_info >= (3, 10)
 PYPY = platform.python_implementation() == "PyPy"
@@ -117,7 +123,7 @@ def is_ci_environment() -> bool:
     return os.environ.get("PANDAS_CI", "0") == "1"
 
 
-def get_lzma_file():
+def get_lzma_file() -> type[lzma.LZMAFile]:
     """
     Importing the `LZMAFile` class from the `lzma` module.
 
diff --git a/pandas/compat/pickle_compat.py b/pandas/compat/pickle_compat.py
index 2333324a7e22d..c8db82500d0d6 100644
--- a/pandas/compat/pickle_compat.py
+++ b/pandas/compat/pickle_compat.py
@@ -7,7 +7,10 @@
 import copy
 import io
 import pickle as pkl
-from typing import TYPE_CHECKING
+from typing import (
+    TYPE_CHECKING,
+    Iterator,
+)
 import warnings
 
 import numpy as np
@@ -291,7 +294,7 @@ def loads(
 
 
 @contextlib.contextmanager
-def patch_pickle():
+def patch_pickle() -> Iterator[None]:
     """
     Temporarily patch pickle to use our unpickler.
     """
diff --git a/pandas/conftest.py b/pandas/conftest.py
index dfe8c5f1778d3..eb17aac99a904 100644
--- a/pandas/conftest.py
+++ b/pandas/conftest.py
@@ -29,6 +29,10 @@
 from decimal import Decimal
 import operator
 import os
+from typing import (
+    Callable,
+    Literal,
+)
 
 from dateutil.tz import (
     tzlocal,
@@ -90,7 +94,7 @@
 # pytest
 
 
-def pytest_addoption(parser):
+def pytest_addoption(parser) -> None:
     parser.addoption("--skip-slow", action="store_true", help="skip slow tests")
     parser.addoption("--skip-network", action="store_true", help="skip network tests")
     parser.addoption("--skip-db", action="store_true", help="skip db tests")
@@ -231,7 +235,7 @@ def pytest_collection_modifyitems(items, config):
 
 
 @pytest.fixture
-def add_doctest_imports(doctest_namespace):
+def add_doctest_imports(doctest_namespace) -> None:
     """
     Make `np` and `pd` names available for doctests.
     """
@@ -243,7 +247,7 @@ def add_doctest_imports(doctest_namespace):
 # Autouse fixtures
 # ----------------------------------------------------------------
 @pytest.fixture(autouse=True)
-def configure_tests():
+def configure_tests() -> None:
     """
     Configure settings for all tests and test modules.
     """
@@ -530,7 +534,7 @@ def multiindex_year_month_day_dataframe_random_data():
 
 
 @pytest.fixture
-def lexsorted_two_level_string_multiindex():
+def lexsorted_two_level_string_multiindex() -> MultiIndex:
     """
     2-level MultiIndex, lexsorted, with string names.
     """
@@ -542,7 +546,9 @@ def lexsorted_two_level_string_multiindex():
 
 
 @pytest.fixture
-def multiindex_dataframe_random_data(lexsorted_two_level_string_multiindex):
+def multiindex_dataframe_random_data(
+    lexsorted_two_level_string_multiindex,
+) -> DataFrame:
     """DataFrame with 2 level MultiIndex with random data"""
     index = lexsorted_two_level_string_multiindex
     return DataFrame(
@@ -715,7 +721,7 @@ def index_with_missing(request):
 # Series'
 # ----------------------------------------------------------------
 @pytest.fixture
-def string_series():
+def string_series() -> Series:
     """
     Fixture for Series of floats with Index of unique strings
     """
@@ -725,7 +731,7 @@ def string_series():
 
 
 @pytest.fixture
-def object_series():
+def object_series() -> Series:
     """
     Fixture for Series of dtype object with Index of unique strings
     """
@@ -735,7 +741,7 @@ def object_series():
 
 
 @pytest.fixture
-def datetime_series():
+def datetime_series() -> Series:
     """
     Fixture for Series of floats with DatetimeIndex
     """
@@ -758,7 +764,7 @@ def _create_series(index):
 
 
 @pytest.fixture
-def series_with_simple_index(index):
+def series_with_simple_index(index) -> Series:
     """
     Fixture for tests on series with changing types of indices.
     """
@@ -766,7 +772,7 @@ def series_with_simple_index(index):
 
 
 @pytest.fixture
-def series_with_multilevel_index():
+def series_with_multilevel_index() -> Series:
     """
     Fixture with a Series with a 2-level MultiIndex.
     """
@@ -804,7 +810,7 @@ def index_or_series_obj(request):
 # DataFrames
 # ----------------------------------------------------------------
 @pytest.fixture
-def int_frame():
+def int_frame() -> DataFrame:
     """
     Fixture for DataFrame of ints with index of unique strings
 
@@ -833,7 +839,7 @@ def int_frame():
 
 
 @pytest.fixture
-def datetime_frame():
+def datetime_frame() -> DataFrame:
     """
     Fixture for DataFrame of floats with DatetimeIndex
 
@@ -862,7 +868,7 @@ def datetime_frame():
 
 
 @pytest.fixture
-def float_frame():
+def float_frame() -> DataFrame:
     """
     Fixture for DataFrame of floats with index of unique strings
 
@@ -891,7 +897,7 @@ def float_frame():
 
 
 @pytest.fixture
-def mixed_type_frame():
+def mixed_type_frame() -> DataFrame:
     """
     Fixture for DataFrame of float/int/string columns with RangeIndex
     Columns are ['a', 'b', 'c', 'float32', 'int32'].
@@ -909,7 +915,7 @@ def mixed_type_frame():
 
 
 @pytest.fixture
-def rand_series_with_duplicate_datetimeindex():
+def rand_series_with_duplicate_datetimeindex() -> Series:
     """
     Fixture for Series with a DatetimeIndex that has duplicates.
     """
@@ -1151,7 +1157,7 @@ def strict_data_files(pytestconfig):
 
 
 @pytest.fixture
-def datapath(strict_data_files):
+def datapath(strict_data_files: str) -> Callable[..., str]:
     """
     Get the path to a data file.
 
@@ -1186,7 +1192,7 @@ def deco(*args):
 
 
 @pytest.fixture
-def iris(datapath):
+def iris(datapath) -> DataFrame:
     """
     The iris dataset as a DataFrame.
     """
@@ -1376,7 +1382,7 @@ def timedelta64_dtype(request):
 
 
 @pytest.fixture
-def fixed_now_ts():
+def fixed_now_ts() -> Timestamp:
     """
     Fixture emits fixed Timestamp.now()
     """
@@ -1845,7 +1851,7 @@ def using_array_manager():
 
 
 @pytest.fixture
-def using_copy_on_write():
+def using_copy_on_write() -> Literal[False]:
     """
     Fixture to check if Copy-on-Write is enabled.
     """
diff --git a/pandas/io/common.py b/pandas/io/common.py
index ef8b466145daa..d911499aa848e 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -821,7 +821,10 @@ def get_handle(
 
         # XZ Compression
         elif compression == "xz":
-            handle = get_lzma_file()(handle, ioargs.mode)
+            # error: Argument 1 to "LZMAFile" has incompatible type "Union[str,
+            # BaseBuffer]"; expected "Optional[Union[Union[str, bytes, PathLike[str],
+            # PathLike[bytes]], IO[bytes]]]"
+            handle = get_lzma_file()(handle, ioargs.mode)  # type: ignore[arg-type]
 
         # Zstd Compression
         elif compression == "zstd":
diff --git a/pandas/tests/api/test_api.py b/pandas/tests/api/test_api.py
index bfdf3eb6992ca..6350f402ac0e5 100644
--- a/pandas/tests/api/test_api.py
+++ b/pandas/tests/api/test_api.py
@@ -16,7 +16,9 @@ def check(self, namespace, expected, ignored=None):
         # ignored ones
         # compare vs the expected
 
-        result = sorted(f for f in dir(namespace) if not f.startswith("__"))
+        result = sorted(
+            f for f in dir(namespace) if not f.startswith("__") and f != "annotations"
+        )
         if ignored is not None:
             result = sorted(set(result) - set(ignored))
 
diff --git a/pandas/tests/util/test_assert_attr_equal.py b/pandas/tests/util/test_assert_attr_equal.py
index 115ef58e085cc..bbbb0bf2172b1 100644
--- a/pandas/tests/util/test_assert_attr_equal.py
+++ b/pandas/tests/util/test_assert_attr_equal.py
@@ -10,7 +10,7 @@
 def test_assert_attr_equal(nulls_fixture):
     obj = SimpleNamespace()
     obj.na_value = nulls_fixture
-    assert tm.assert_attr_equal("na_value", obj, obj)
+    tm.assert_attr_equal("na_value", obj, obj)
 
 
 def test_assert_attr_equal_different_nulls(nulls_fixture, nulls_fixture2):
@@ -21,13 +21,13 @@ def test_assert_attr_equal_different_nulls(nulls_fixture, nulls_fixture2):
     obj2.na_value = nulls_fixture2
 
     if nulls_fixture is nulls_fixture2:
-        assert tm.assert_attr_equal("na_value", obj, obj2)
+        tm.assert_attr_equal("na_value", obj, obj2)
     elif is_float(nulls_fixture) and is_float(nulls_fixture2):
         # we consider float("nan") and np.float64("nan") to be equivalent
-        assert tm.assert_attr_equal("na_value", obj, obj2)
+        tm.assert_attr_equal("na_value", obj, obj2)
     elif type(nulls_fixture) is type(nulls_fixture2):
         # e.g. Decimal("NaN")
-        assert tm.assert_attr_equal("na_value", obj, obj2)
+        tm.assert_attr_equal("na_value", obj, obj2)
     else:
         with pytest.raises(AssertionError, match='"na_value" are different'):
             tm.assert_attr_equal("na_value", obj, obj2)
diff --git a/pyright_reportGeneralTypeIssues.json b/pyright_reportGeneralTypeIssues.json
index 541ae4b198166..98da481a6d80f 100644
--- a/pyright_reportGeneralTypeIssues.json
+++ b/pyright_reportGeneralTypeIssues.json
@@ -16,6 +16,7 @@
         "pandas/util/version",
         # and all files that currently don't pass
         "pandas/_config/config.py",
+        "pandas/_testing/__init__.py",
         "pandas/core/algorithms.py",
         "pandas/core/apply.py",
         "pandas/core/array_algos/take.py",