MAINT: drop Python 3.8 support due to EOL

docs/conf.py

@@ -40,13 +40,15 @@
     "ampform_dpd.decay.StateIDTemplate": ("obj", "ampform_dpd.decay.StateID"),
     "ampform_dpd.io.serialization.dynamics.T": "typing.TypeVar",
     "DecayNode": ("obj", "ampform_dpd.decay.DecayNode"),
+    "EdgeType": "typing.TypeVar",
     "FinalState": ("obj", "ampform_dpd.decay.FinalState"),
     "FinalStateID": ("obj", "ampform_dpd.decay.FinalStateID"),
     "FrozenTransition": "qrules.topology.FrozenTransition",
     "InitialStateID": ("obj", "ampform_dpd.decay.InitialStateID"),
     "Literal[-1, 1]": "typing.Literal",
     "Literal[(-1, 1)]": "typing.Literal",
     "Node": ("obj", "ampform_dpd.io.serialization.format.Node"),
+    "NodeType": "typing.TypeVar",
     "ParameterValue": ("obj", "tensorwaves.interface.ParameterValue"),
     "ParametrizedBackendFunction": "tensorwaves.function.ParametrizedBackendFunction",
     "PoolSum": "ampform.sympy.PoolSum",
@@ -172,7 +174,7 @@
 html_title = REPO_TITLE
 intersphinx_mapping = {
     "IPython": (f"https://ipython.readthedocs.io/en/{pin('IPython')}", None),
-    "ampform": (f"https://ampform.readthedocs.io/en/{pin('ampform')}", None),
+    "ampform": (f"https://ampform.readthedocs.io/{pin('ampform')}", None),
     "attrs": (f"https://www.attrs.org/en/{pin('attrs')}", None),
     "compwa": ("https://compwa.github.io", None),
     "graphviz": ("https://graphviz.readthedocs.io/en/stable", None),
@@ -181,17 +183,14 @@
     "matplotlib": (f"https://matplotlib.org/{pin('matplotlib')}", None),
     "numpy": (f"https://numpy.org/doc/{pin_minor('numpy')}", None),
     "python": ("https://docs.python.org/3", None),
-    "qrules": (f"https://qrules.readthedocs.io/en/{pin('qrules')}", None),
+    "qrules": (f"https://qrules.readthedocs.io/{pin('qrules')}", None),
     "sympy": ("https://docs.sympy.org/latest", None),
-    "tensorwaves": (
-        f"https://tensorwaves.readthedocs.io/en/{pin('tensorwaves')}",
-        None,
-    ),
+    "tensorwaves": (f"https://tensorwaves.readthedocs.io/{pin('tensorwaves')}", None),
 }
 linkcheck_anchors = False
 linkcheck_ignore = [
-    "https://github.com/ComPWA/polarimetry",
-    "https://journals.aps.org/prd/pdf/10.1103/PhysRevD.101.034033#page=9",
+    "https://doi.org/10.1103",
+    "https://journals.aps.org/prd",
 ]
 myst_enable_extensions = [
     "amsmath",

pyproject.toml

@@ -18,7 +18,6 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
-    "Programming Language :: Python :: 3.8",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python",
     "Topic :: Scientific/Engineering :: Physics",
@@ -38,7 +37,7 @@ description = "Symbolic expressions for Dalitz-Plot Decomposition"
 dynamic = ["version"]
 license = {file = "LICENSE"}
 name = "ampform-dpd"
-requires-python = ">=3.8"
+requires-python = ">=3.9"
 
 [project.optional-dependencies]
 dev = [

src/ampform_dpd/__init__.py

@@ -3,7 +3,7 @@
 from __future__ import annotations
 
 from collections import abc
-from functools import lru_cache
+from functools import cache
 from itertools import product
 from typing import Any, Literal, Protocol
 from warnings import warn
@@ -289,7 +289,7 @@ def _create_coupling_symbol(
     return H[resonance, interaction.L, interaction.S]
 
 
-@lru_cache(maxsize=None)
+@cache
 def _get_coupling_base(
     helicity_coupling: bool, typ: Literal["production", "decay"]
 ) -> sp.IndexedBase:
@@ -331,7 +331,7 @@ def _formulate_clebsch_gordan_factors(
     return sqrt_factor * cg_ll * cg_ss
 
 
-@lru_cache(maxsize=None)
+@cache
 def _generate_amplitude_index_bases() -> dict[FinalStateID, sp.IndexedBase]:
     return dict(enumerate(sp.symbols(R"A^(1:4)", cls=sp.IndexedBase), 1))  # type:ignore[arg-type]
 

src/ampform_dpd/_attrs.py

@@ -2,11 +2,13 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Iterable, SupportsFloat
+from typing import TYPE_CHECKING, SupportsFloat
 
 import sympy as sp
 
 if TYPE_CHECKING:
+    from collections.abc import Iterable
+
     from attrs import Attribute
 
     from ampform_dpd.decay import LSCoupling, ThreeBodyDecayChain

src/ampform_dpd/_cache.py

@@ -80,7 +80,7 @@ def _get_python_hash_seed() -> int | None:
     return None
 
 
-@functools.lru_cache(maxsize=None)  # warn once
+@functools.cache  # warn once
 def _warn_about_unsafe_hash() -> None:
     message = """
     PYTHONHASHSEED has not been set. For faster and safer hashing of SymPy expressions,

src/ampform_dpd/adapter/qrules.py

@@ -5,7 +5,7 @@
 from collections import abc, defaultdict
 from functools import singledispatch
 from pathlib import Path
-from typing import Any, Iterable, NoReturn, TypeVar, overload
+from typing import TYPE_CHECKING, Any, NoReturn, TypeVar, overload
 
 import attrs
 import qrules
@@ -24,6 +24,9 @@
     ThreeBodyDecayChain,
 )
 
+if TYPE_CHECKING:
+    from collections.abc import Iterable
+
 _LOGGER = logging.getLogger(__name__)