Drop support for Python 3.9, require Python >= 3.10 (#2132)

* Drop support for Python 3.9, require Python >= 3.10

Starting development for Mesa 3.0 and following SPEC 0 we can drop Python 3.9 support and require Python 3.10 or higher for future development. This allows adopting more modern Python features and simplifies the testing and CI configurations.

See the Python 3.10 release notes: https://docs.python.org/3/whatsnew/3.10.html

The 2.3.x release series will keep supporting Python 3.9.

* Update type hinting for Python 3.10

`X | Y` can now be used for type annotations, including making a variable optional with `X | None`

* intro_tutorial.ipynb: Require Python 3.10

* typing: Replace Union with pipe (|)

We can do this now in Python 3.10!

.github/workflows/build_lint.yml

@@ -37,8 +37,6 @@ jobs:
             python-version: "3.11"
           - os: ubuntu
             python-version: "3.10"
-          - os: ubuntu
-            python-version: "3.9"
           # Disabled for now. See https://github.com/projectmesa/mesa/issues/1253
           #- os: ubuntu
           #  python-version: 'pypy-3.8'

.pre-commit-config.yaml

@@ -17,7 +17,7 @@ repos:
     rev: v3.15.2
     hooks:
     -   id: pyupgrade
-        args: [--py38-plus]
+        args: [--py310-plus]
 -   repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v4.5.0  # Use the ref you want to point at
     hooks:

docs/tutorials/intro_tutorial.ipynb

@@ -60,7 +60,7 @@
    "source": [
     "### Tutorial Setup\n",
     "\n",
-    "Create and activate a [virtual environment](http://docs.python-guide.org/en/latest/dev/virtualenvs/). *Python version 3.9 or higher is required*.\n",
+    "Create and activate a [virtual environment](http://docs.python-guide.org/en/latest/dev/virtualenvs/). *Python version 3.10 or higher is required*.\n",
     "\n",
     "Install Mesa:\n",
     "\n",

mesa/agent.py

@@ -14,11 +14,11 @@
 import warnings
 import weakref
 from collections import defaultdict
-from collections.abc import Iterable, Iterator, MutableSet, Sequence
+from collections.abc import Callable, Iterable, Iterator, MutableSet, Sequence
 from random import Random
 
 # mypy
-from typing import TYPE_CHECKING, Any, Callable
+from typing import TYPE_CHECKING, Any
 
 if TYPE_CHECKING:
     # We ensure that these are not imported during runtime to prevent cyclic

mesa/batchrunner.py

@@ -2,7 +2,7 @@
 from collections.abc import Iterable, Mapping
 from functools import partial
 from multiprocessing import Pool
-from typing import Any, Optional, Union
+from typing import Any
 
 from tqdm.auto import tqdm
 
@@ -11,9 +11,9 @@
 
 def batch_run(
     model_cls: type[Model],
-    parameters: Mapping[str, Union[Any, Iterable[Any]]],
+    parameters: Mapping[str, Any | Iterable[Any]],
     # We still retain the Optional[int] because users may set it to None (i.e. use all CPUs)
-    number_processes: Optional[int] = 1,
+    number_processes: int | None = 1,
     iterations: int = 1,
     data_collection_period: int = -1,
     max_steps: int = 1000,
@@ -76,7 +76,7 @@ def batch_run(
 
 
 def _make_model_kwargs(
-    parameters: Mapping[str, Union[Any, Iterable[Any]]],
+    parameters: Mapping[str, Any | Iterable[Any]],
 ) -> list[dict[str, Any]]:
     """Create model kwargs from parameters dictionary.
 

mesa/datacollection.py

@@ -196,7 +196,7 @@ def collect(self, model):
         if self.model_reporters:
             for var, reporter in self.model_reporters.items():
                 # Check if lambda or partial function
-                if isinstance(reporter, (types.LambdaType, partial)):
+                if isinstance(reporter, types.LambdaType | partial):
                     self.model_vars[var].append(reporter(model))
                 # Check if model attribute
                 elif isinstance(reporter, str):

mesa/experimental/cell_space/cell_collection.py

@@ -1,10 +1,10 @@
 from __future__ import annotations
 
 import itertools
-from collections.abc import Iterable, Mapping
+from collections.abc import Callable, Iterable, Mapping
 from functools import cached_property
 from random import Random
-from typing import TYPE_CHECKING, Callable, Generic, TypeVar
+from typing import TYPE_CHECKING, Generic, TypeVar
 
 if TYPE_CHECKING:
     from mesa.experimental.cell_space.cell import Cell

mesa/experimental/cell_space/grid.py

@@ -60,7 +60,7 @@ def _validate_parameters(self):
             raise ValueError("Dimensions must be a list of positive integers.")
         if not isinstance(self.torus, bool):
             raise ValueError("Torus must be a boolean.")
-        if self.capacity is not None and not isinstance(self.capacity, (float, int)):
+        if self.capacity is not None and not isinstance(self.capacity, float | int):
             raise ValueError("Capacity must be a number or None.")
 
     def select_random_empty_cell(self) -> T:

mesa/experimental/cell_space/network.py

@@ -1,5 +1,5 @@
 from random import Random
-from typing import Any, Optional
+from typing import Any
 
 from mesa.experimental.cell_space.cell import Cell
 from mesa.experimental.cell_space.discrete_space import DiscreteSpace
@@ -11,8 +11,8 @@ class Network(DiscreteSpace):
     def __init__(
         self,
         G: Any,  # noqa: N803
-        capacity: Optional[int] = None,
-        random: Optional[Random] = None,
+        capacity: int | None = None,
+        random: Random | None = None,
         cell_klass: type[Cell] = Cell,
     ) -> None:
         """A Networked grid

mesa/experimental/components/altair.py

@@ -1,5 +1,4 @@
 import contextlib
-from typing import Optional
 
 import solara
 
@@ -8,7 +7,7 @@
 
 
 @solara.component
-def SpaceAltair(model, agent_portrayal, dependencies: Optional[list[any]] = None):
+def SpaceAltair(model, agent_portrayal, dependencies: list[any] | None = None):
     space = getattr(model, "grid", None)
     if space is None:
         # Sometimes the space is defined as model.space instead of model.grid

mesa/experimental/components/matplotlib.py

@@ -1,5 +1,3 @@
-from typing import Optional
-
 import networkx as nx
 import solara
 from matplotlib.figure import Figure
@@ -9,7 +7,7 @@
 
 
 @solara.component
-def SpaceMatplotlib(model, agent_portrayal, dependencies: Optional[list[any]] = None):
+def SpaceMatplotlib(model, agent_portrayal, dependencies: list[any] | None = None):
     space_fig = Figure()
     space_ax = space_fig.subplots()
     space = getattr(model, "grid", None)
@@ -116,7 +114,7 @@ def portray(space):
 
 
 @solara.component
-def PlotMatplotlib(model, measure, dependencies: Optional[list[any]] = None):
+def PlotMatplotlib(model, measure, dependencies: list[any] | None = None):
     fig = Figure()
     ax = fig.subplots()
     df = model.datacollector.get_model_vars_dataframe()
@@ -127,7 +125,7 @@ def PlotMatplotlib(model, measure, dependencies: Optional[list[any]] = None):
         for m, color in measure.items():
             ax.plot(df.loc[:, m], label=m, color=color)
         fig.legend()
-    elif isinstance(measure, (list, tuple)):
+    elif isinstance(measure, list | tuple):
         for m in measure:
             ax.plot(df.loc[:, m], label=m)
         fig.legend()

mesa/experimental/devs/eventlist.py

@@ -1,10 +1,11 @@
 from __future__ import annotations
 
 import itertools
+from collections.abc import Callable
 from enum import IntEnum
 from heapq import heapify, heappop, heappush
 from types import MethodType
-from typing import Any, Callable
+from typing import Any
 from weakref import WeakMethod, ref
 
 

mesa/experimental/devs/simulator.py

@@ -1,7 +1,8 @@
 from __future__ import annotations
 
 import numbers
-from typing import Any, Callable
+from collections.abc import Callable
+from typing import Any
 
 from mesa import Model
 

mesa/model.py

@@ -14,12 +14,12 @@
 from collections import defaultdict
 
 # mypy
-from typing import Any, Union
+from typing import Any
 
 from mesa.agent import Agent, AgentSet
 from mesa.datacollection import DataCollector
 
-TimeT = Union[float, int]
+TimeT = float | int
 
 
 class Model:

mesa/space.py

@@ -23,9 +23,9 @@
 import itertools
 import math
 import warnings
-from collections.abc import Iterable, Iterator, Sequence
+from collections.abc import Callable, Iterable, Iterator, Sequence
 from numbers import Real
-from typing import Any, Callable, TypeVar, Union, cast, overload
+from typing import Any, TypeVar, cast, overload
 from warnings import warn
 
 with contextlib.suppress(ImportError):
@@ -42,12 +42,12 @@
 
 Coordinate = tuple[int, int]
 # used in ContinuousSpace
-FloatCoordinate = Union[tuple[float, float], npt.NDArray[float]]
+FloatCoordinate = tuple[float, float] | npt.NDArray[float]
 NetworkCoordinate = int
 
-Position = Union[Coordinate, FloatCoordinate, NetworkCoordinate]
+Position = Coordinate | FloatCoordinate | NetworkCoordinate
 
-GridContent = Union[Agent, None]
+GridContent = Agent | None
 MultiGridContent = list[Agent]
 
 F = TypeVar("F", bound=Callable[..., Any])

mesa/time.py

@@ -30,14 +30,12 @@
 from collections.abc import Iterable
 
 # mypy
-from typing import Union
-
 from mesa.agent import Agent, AgentSet
 from mesa.model import Model
 
 # BaseScheduler has a self.time of int, while
 # StagedActivation has a self.time of float
-TimeT = Union[float, int]
+TimeT = float | int
 
 
 class BaseScheduler:

pyproject.toml

@@ -6,7 +6,7 @@ build-backend = "hatchling.build"
 name = "Mesa"
 description = "Agent-based modeling (ABM) in Python"
 license = { text = "Apache 2.0" }
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 authors = [
   { name = "Project Mesa Team", email = "[email protected]" },
 ]
@@ -25,7 +25,6 @@ classifiers = [
   "Topic :: Scientific/Engineering :: Artificial Intelligence",
   "Intended Audience :: Science/Research",
   "Programming Language :: Python :: 3 :: Only",
-  "Programming Language :: Python :: 3.9",
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
@@ -81,9 +80,9 @@ path = "mesa/__init__.py"
 
 [tool.ruff]
 # See https://github.com/charliermarsh/ruff#rules for error code definitions.
-# Hardcode to Python 3.9.
+# Hardcode to Python 3.10.
 # Reminder to update mesa-examples if the value below is changed.
-target-version = "py39"
+target-version = "py310"
 extend-exclude = ["docs", "build"]
 
 [tool.ruff.lint]