build: Drop support for Python 3.8 (#2625)

matthewfeickert · kratsg · web-flow · commit 157fc959a161 · 2025-11-05T21:35:25.000+01:00
* Support Python 3.9+, dropping support for Python 3.8.
* Simplify code by removing components that existed to support pre Python 3.9
  features or solutions.
* Use improved typing features from Python 3.9.
* Remove importlib_resources conditional dependency for Python &lt; 3.9.
* Remove Python 3.8 trove classifier.
* Use Python 3.10 for the mypy minimum python check, due to Numpy typing being
  improved in 3.10+.

Co-authored-by: Giordon Stark &lt;kratsg@gmail.com&gt;
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -30,7 +30,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
+        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13']
         include:
           - os: macos-latest
             python-version: '3.13'
diff --git a/.github/workflows/lower-bound-requirements.yml b/.github/workflows/lower-bound-requirements.yml
@@ -17,7 +17,7 @@ jobs:
       matrix:
         os: [ubuntu-latest]
         # minimum supported Python
-        python-version: ['3.8']
+        python-version: ['3.9']
 
     steps:
     - uses: actions/checkout@v5
diff --git a/.github/workflows/release_tests.yml b/.github/workflows/release_tests.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
+        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13']
         include:
           - os: macos-latest
             python-version: '3.13'
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
@@ -55,14 +55,15 @@ repos:
 -   repo: https://github.com/pre-commit/mirrors-mypy
     rev: v1.13.0
     # check the oldest and newest supported Pythons
+    # except skip python 3.9 for numpy, due to poor typing
     hooks:
       - &mypy
         id: mypy
-        name: mypy with Python 3.8
+        name: mypy with Python 3.10
         files: src
         additional_dependencies:
           ['numpy', 'types-tqdm', 'click', 'types-jsonpatch', 'types-pyyaml', 'types-jsonschema', 'importlib_metadata', 'packaging']
-        args: ["--python-version=3.8"]
+        args: ["--python-version=3.10"]
       - <<: *mypy
         name: mypy with Python 3.13
         args: ["--python-version=3.13"]
diff --git a/pyproject.toml b/pyproject.toml
@@ -11,7 +11,7 @@ dynamic = ["version"]
 description = "pure-Python HistFactory implementation with tensors and autodiff"
 readme = "README.rst"
 license = "Apache-2.0"
-requires-python = ">=3.8"
+requires-python = ">=3.9"
 authors = [
     { name = "Lukas Heinrich", email = "lukas.heinrich@cern.ch" },
     { name = "Matthew Feickert", email = "matthew.feickert@cern.ch" },
@@ -32,7 +32,6 @@ classifiers = [
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3 :: Only",
-    "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
@@ -44,7 +43,6 @@ classifiers = [
 ]
 dependencies = [
     "click>=8.0.0",  # for console scripts
-    "importlib_resources>=1.4.0; python_version < '3.9'",  # for resources in schema
     "jsonpatch>=1.15",
     "jsonschema>=4.15.0",  # for utils
     "pyyaml>=5.1",  # for parsing CLI equal-delimited options
diff --git a/src/pyhf/contrib/utils.py b/src/pyhf/contrib/utils.py
@@ -80,13 +80,7 @@ def download(archive_url, output_directory, force=False, compress=False):
                 with open(output_directory, "wb") as archive:
                     archive.write(response.content)
             else:
-                # Support for file-like objects for tarfile.is_tarfile was added
-                # in Python 3.9, so as pyhf is currently Python 3.8+ then can't
-                # do tarfile.is_tarfile(BytesIO(response.content)).
-                # Instead, just use a 'try except' block to determine if the
-                # archive is a valid tarfile.
-                # TODO: Simplify after pyhf is Python 3.9+ only
-                try:
+                if tarfile.is_tarfile(BytesIO(response.content)):
                     # Use transparent compression to allow for .tar or .tar.gz
                     with tarfile.open(
                         mode="r:*", fileobj=BytesIO(response.content)
@@ -97,13 +91,7 @@ def download(archive_url, output_directory, force=False, compress=False):
                             archive.extractall(output_directory, filter="data")
                         else:
                             archive.extractall(output_directory)
-                except tarfile.ReadError:
-                    if not zipfile.is_zipfile(BytesIO(response.content)):
-                        raise exceptions.InvalidArchive(
-                            f"The archive downloaded from {archive_url} is not a tarfile"
-                            + " or a zipfile and so can not be opened as one."
-                        )
-
+                elif zipfile.is_zipfile(BytesIO(response.content)):
                     output_directory = Path(output_directory)
                     if output_directory.exists():
                         rmtree(output_directory)
@@ -129,6 +117,11 @@ def download(archive_url, output_directory, force=False, compress=False):
                         # from creation time
                         rmtree(output_directory)
                         _tmp_path.replace(output_directory)
+                else:
+                    raise exceptions.InvalidArchive(
+                        f"The archive downloaded from {archive_url} is not a tarfile"
+                        + " or a zipfile and so can not be opened as one."
+                    )
 
 except ModuleNotFoundError:
     log.error(
diff --git a/src/pyhf/mixins.py b/src/pyhf/mixins.py
@@ -1,7 +1,8 @@
 from __future__ import annotations
 
 import logging
-from typing import Any, Sequence
+from typing import Any
+from collections.abc import Sequence
 
 from pyhf.typing import Channel
 
diff --git a/src/pyhf/modifiers/staterror.py b/src/pyhf/modifiers/staterror.py
@@ -1,5 +1,4 @@
 import logging
-from typing import List
 
 import pyhf
 from pyhf import events
@@ -10,7 +9,7 @@
 log = logging.getLogger(__name__)
 
 
-def required_parset(sigmas, fixed: List[bool]):
+def required_parset(sigmas, fixed: list[bool]):
     n_parameters = len(sigmas)
     return {
         'paramset_type': 'constrained_by_normal',
diff --git a/src/pyhf/parameters/paramsets.py b/src/pyhf/parameters/paramsets.py
@@ -1,5 +1,3 @@
-from typing import List
-
 import pyhf
 
 __all__ = [
@@ -29,7 +27,7 @@ def __init__(self, **kwargs):
             )
 
     @property
-    def suggested_fixed(self) -> List[bool]:
+    def suggested_fixed(self) -> list[bool]:
         if isinstance(self._suggested_fixed, bool):
             return [self._suggested_fixed] * self.n_parameters
         return self._suggested_fixed
diff --git a/src/pyhf/pdf.py b/src/pyhf/pdf.py
@@ -2,7 +2,7 @@
 
 import copy
 import logging
-from typing import List, Union
+from typing import Union
 
 import pyhf.parameters
 import pyhf
@@ -406,7 +406,7 @@ def param_set(self, name):
         """
         return self.par_map[name]['paramset']
 
-    def suggested_fixed(self) -> List[bool]:
+    def suggested_fixed(self) -> list[bool]:
         """
         Identify the fixed parameters in the model.
 
diff --git a/src/pyhf/readxml.py b/src/pyhf/readxml.py
@@ -4,16 +4,10 @@
 from typing import (
     IO,
     Callable,
-    Iterable,
-    List,
-    MutableMapping,
-    MutableSequence,
-    Sequence,
-    Set,
-    Tuple,
     Union,
     cast,
 )
+from collections.abc import Iterable, MutableMapping, MutableSequence, Sequence
 
 import xml.etree.ElementTree as ET
 from pathlib import Path
@@ -46,8 +40,8 @@
 
 log = logging.getLogger(__name__)
 
-FileCacheType = MutableMapping[str, Tuple[Union[IO[str], IO[bytes]], Set[str]]]
-MountPathType = Iterable[Tuple[Path, Path]]
+FileCacheType = MutableMapping[str, tuple[Union[IO[str], IO[bytes]], set[str]]]
+MountPathType = Iterable[tuple[Path, Path]]
 ResolverType = Callable[[str], Path]
 
 __FILECACHE__: FileCacheType = {}
@@ -99,7 +93,7 @@ def extract_error(hist: uproot.behaviors.TH1.TH1) -> list[float]:
     """
 
     variance = hist.variances() if hist.weighted else hist.to_numpy()[0]
-    return cast(List[float], np.sqrt(variance).tolist())
+    return cast(list[float], np.sqrt(variance).tolist())
 
 
 def import_root_histogram(
diff --git a/src/pyhf/schema/loader.py b/src/pyhf/schema/loader.py
@@ -1,15 +1,8 @@
 from pathlib import Path
-import sys
 import json
 import pyhf.exceptions
 from pyhf.schema import variables
-
-# importlib.resources.as_file wasn't added until Python 3.9
-# c.f. https://docs.python.org/3.9/library/importlib.html#importlib.resources.as_file
-if sys.version_info >= (3, 9):
-    from importlib import resources
-else:
-    import importlib_resources as resources
+from importlib import resources
 
 
 def load_schema(schema_id: str):
diff --git a/src/pyhf/schema/validator.py b/src/pyhf/schema/validator.py
@@ -1,6 +1,7 @@
 import numbers
 from pathlib import Path
-from typing import Mapping, Union
+from typing import Union
+from collections.abc import Mapping
 
 import jsonschema
 
diff --git a/src/pyhf/schema/variables.py b/src/pyhf/schema/variables.py
@@ -1,11 +1,5 @@
-import sys
+from importlib import resources
 
-# importlib.resources.as_file wasn't added until Python 3.9
-# c.f. https://docs.python.org/3.9/library/importlib.html#importlib.resources.as_file
-if sys.version_info >= (3, 9):
-    from importlib import resources
-else:
-    import importlib_resources as resources
 schemas = resources.files('pyhf') / "schemas"
 
 SCHEMA_CACHE = {}
diff --git a/src/pyhf/tensor/numpy_backend.py b/src/pyhf/tensor/numpy_backend.py
@@ -3,7 +3,8 @@
 from __future__ import annotations
 
 import logging
-from typing import TYPE_CHECKING, Callable, Generic, Mapping, Sequence, TypeVar, Union
+from typing import TYPE_CHECKING, Callable, Generic, TypeVar, Union
+from collections.abc import Mapping, Sequence
 
 import numpy as np
 
@@ -207,7 +208,8 @@ def conditional(
 
     def tolist(self, tensor_in: Tensor[T] | list[T]) -> list[T]:
         try:
-            return tensor_in.tolist()  # type: ignore[union-attr,no-any-return]
+            # unused-ignore for [no-any-return] in python 3.9
+            return tensor_in.tolist()  # type: ignore[union-attr,no-any-return,unused-ignore]
         except AttributeError:
             if isinstance(tensor_in, list):
                 return tensor_in
@@ -654,4 +656,5 @@ def transpose(self, tensor_in: Tensor[T]) -> ArrayLike:
 
         .. versionadded:: 0.7.0
         """
-        return tensor_in.transpose()
+        # TODO: Casting needed for Python 3.10 mypy but not Python 3.13?
+        return cast(ArrayLike, tensor_in.transpose())
diff --git a/src/pyhf/typing.py b/src/pyhf/typing.py
@@ -2,14 +2,12 @@
 from typing import (
     Any,
     Literal,
-    MutableSequence,
     Protocol,
-    Sequence,
     SupportsIndex,
-    Tuple,
     TypedDict,
     Union,
 )
+from collections.abc import MutableSequence, Sequence
 
 __all__ = (
     "Channel",
@@ -35,10 +33,9 @@
 )
 
 
-# TODO: Switch to os.PathLike[str] once Python 3.8 support dropped
-PathOrStr = Union[str, "os.PathLike[str]"]
+PathOrStr = Union[str, os.PathLike[str]]
 
-Shape = Tuple[int, ...]
+Shape = tuple[int, ...]
 ShapeLike = Union[SupportsIndex, Sequence[SupportsIndex]]
 
 
diff --git a/src/pyhf/utils.py b/src/pyhf/utils.py
@@ -4,14 +4,7 @@
 import hashlib
 from gettext import gettext
 
-import sys
-
-# importlib.resources.as_file wasn't added until Python 3.9
-# c.f. https://docs.python.org/3.9/library/importlib.html#importlib.resources.as_file
-if sys.version_info >= (3, 9):
-    from importlib import resources
-else:
-    import importlib_resources as resources
+from importlib import resources
 
 __all__ = [
     "EqDelimStringParamType",
diff --git a/tests/contrib/test_viz.py b/tests/contrib/test_viz.py
@@ -1,5 +1,4 @@
 import json
-import sys
 
 import matplotlib
 import matplotlib.pyplot as plt
@@ -68,10 +67,6 @@ def test_plot_results(datadir):
 
 
 @pytest.mark.mpl_image_compare
-@pytest.mark.xfail(
-    sys.version_info < (3, 8),
-    reason="baseline image generated with matplotlib v3.6.0 which is Python 3.8+",
-)
 def test_plot_results_no_axis(datadir):
     data = json.load(datadir.joinpath("hypotest_results.json").open(encoding="utf-8"))
 
