BLD: drop support for CPython 3.7

.github/workflows/build-test.yaml

@@ -33,7 +33,7 @@ jobs:
         test-runner: [pytest]
         include:
           - os: ubuntu-latest
-            python-version: '3.7'
+            python-version: '3.8'
             dependencies: minimal
             tests-type: unit
             test-runner: pytest

.github/workflows/type-checking.yaml

@@ -30,7 +30,10 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v3
       with:
-        python-version: '3.7'
+        # run with oldest support python version
+        # so that we always get compatible versions of
+        # core dependencies at type-check time
+        python-version: '3.8'
 
     - name: Build
       run: |

.github/workflows/wheels.yaml

@@ -34,7 +34,7 @@ jobs:
         with:
           output-dir: dist
         env:
-          CIBW_BUILD: "cp37-* cp38-* cp39-* cp310-* cp311-*"
+          CIBW_BUILD: "cp38-* cp39-* cp310-* cp311-*"
           CIBW_SKIP: "*-musllinux_*"  #  numpy doesn't have wheels for musllinux so we can't build some quickly and without bloating
           CIBW_ARCHS_LINUX: "x86_64"
           CIBW_ARCHS_MACOS: x86_64 arm64

.pre-commit-config.yaml

@@ -37,7 +37,7 @@ repos:
     rev: v3.0.0
     hooks:
     - id: pyupgrade
-      args: [--py37-plus]
+      args: [--py38-plus]
 -   repo: https://github.com/psf/black
     rev: 22.10.0
     hooks:
@@ -73,7 +73,7 @@ repos:
   rev: 1.5.2
   hooks:
     - id: nbqa-pyupgrade
-      args: [--py37-plus]
+      args: [--py38-plus]
     - id: nbqa-isort
     - id: nbqa-flake8
       args: [--extend-ignore=E402]

conftest.py

@@ -1,7 +1,7 @@
 import os
 import shutil
-import sys
 import tempfile
+from importlib.metadata import version
 from importlib.util import find_spec
 from pathlib import Path
 
@@ -19,11 +19,6 @@
     data_dir_load,
 )
 
-if sys.version_info >= (3, 8):
-    from importlib.metadata import version
-else:
-    from importlib_metadata import version
-
 MPL_VERSION = Version(version("matplotlib"))
 NUMPY_VERSION = Version(version("numpy"))
 PILLOW_VERSION = Version(version("pillow"))
@@ -95,7 +90,7 @@ def pytest_configure(config):
         "ignore:the imp module is deprecated in favour of importlib and slated for removal in Python 3.12; see the module's documentation for alternative uses:DeprecationWarning",
         # matplotlib warnings related to the Agg backend which is used in CI, not much we can do about it
         "ignore:Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.:UserWarning",
-        "ignore:tight_layout . falling back to Agg renderer:UserWarning",
+        r"ignore:tight_layout.+falling back to Agg renderer:UserWarning",
         #
         # >>> warnings from wrong values passed to numpy
         # these should normally be curated out of the test suite but they are too numerous

doc/source/installing.rst

@@ -32,7 +32,9 @@ Here's a summary for most recent releases
 +------------+------------+----------------+-----------------+
 | yt release | Python 2.7 | Python3 min    | Python3 max     |
 +============+============+================+=================+
-| 4.1.x      | no         | 3.7            | 3.11 (expected) |
+| 4.2.x      | no         | 3.8 (expected) | 3.11 (expected) |
++------------+------------+----------------+-----------------+
+| 4.1.x      | no         | 3.7            | 3.11            |
 +------------+------------+----------------+-----------------+
 | 4.0.x      | no         | 3.6            | 3.10            |
 +------------+------------+----------------+-----------------+

pyproject.toml

@@ -12,7 +12,7 @@ requires = [
 
 [tool.black]
 line-length = 88
-target-version = ['py37']
+target-version = ['py38']
 include = '\.pyi?$'
 exclude = '''
 /(
@@ -134,7 +134,7 @@ ignore = [
 
 
 [tool.mypy]
-python_version = 3.7
+python_version = 3.8
 show_error_codes = true
 ignore_missing_imports = true
 warn_unused_configs = true

setup.cfg

@@ -20,7 +20,6 @@ classifiers =
     Programming Language :: C
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3.10
@@ -38,21 +37,19 @@ project_urls =
 [options]
 packages = find:
 install_requires =
-    cmyt>=0.2.2
+    cmyt>=1.1.2
     ipywidgets>=8.0.0
-    matplotlib!=3.4.2,>=3.1  # keep in sync with tests/windows_conda_requirements.txt
+    matplotlib!=3.4.2,>=3.2  # keep in sync with tests/windows_conda_requirements.txt
     more-itertools>=8.4
-    numpy>=1.14.5
+    numpy>=1.17.5
     packaging>=20.9
-    pillow>=6.2.0 # transitive dependency via MPL (>=3.3)
-    pyparsing>=2.0.2  # transitive dependency via packaging and MPL
+    pillow>=6.2.1 # transitive dependency via MPL (>=3.3)
+    pyparsing>=2.0.3  # transitive dependency via packaging and MPL
     tomli-w>=0.4.0
     tqdm>=3.4.0
-    unyt>=2.8.0,<3.0 # see https://github.com/yt-project/yt/issues/4162
-    importlib-metadata>=1.4;python_version < '3.8'
+    unyt>=2.9.2,<3.0 # see https://github.com/yt-project/yt/issues/4162
     tomli>=1.2.3;python_version < '3.11'
-    typing-extensions>=4.2.0;python_version < '3.8'
-python_requires = >=3.7
+python_requires = >=3.8
 include_package_data = True
 scripts = scripts/iyt
 zip_safe = False
@@ -103,16 +100,15 @@ full =
 mapserver =
     bottle
 minimal =
-    cmyt==0.2.2
+    cmyt==1.1.2
     ipywidgets==8.0.0
-    matplotlib==3.1
+    matplotlib==3.2
     more-itertools==8.4
-    numpy==1.14.5
-    pillow==6.2.0
-    pyparsing==2.0.2
+    numpy==1.17.5
+    pillow==6.2.1
+    pyparsing==2.0.3
     tomli-w==0.4.0
-    unyt==2.8.0
-    importlib-metadata==1.4;python_version < '3.8'
+    unyt==2.9.2
     tomli==1.2.3;python_version < '3.11'
 test =
     nose~=1.3.7

tests/windows_conda_requirements.txt

@@ -2,5 +2,5 @@ numpy>=1.19.4
 cython>=0.29.21,<3.0
 cartopy>=0.21.0
 h5py~=3.1.0
-matplotlib!=3.4.2,>=3.1  # keep in sync with setup.cfg
+matplotlib!=3.4.2,>=3.2  # keep in sync with setup.cfg
 scipy~=1.5.0

yt/_maintenance/backports.py

@@ -20,68 +20,6 @@
 #     from yt._maintenance.backports import cached_property
 import sys
 
-if sys.version_info < (3, 8):
-    from _thread import RLock  # type: ignore
-    from typing import List
-
-    GenericAlias = type(List[int])
-
-    _NOT_FOUND = object()
-
-    class cached_property:
-        def __init__(self, func):
-            self.func = func
-            self.attrname = None
-            self.__doc__ = func.__doc__
-            self.lock = RLock()
-
-        def __set_name__(self, owner, name):
-            if self.attrname is None:
-                self.attrname = name
-            elif name != self.attrname:
-                raise TypeError(
-                    "Cannot assign the same cached_property to two different names "
-                    f"({self.attrname!r} and {name!r})."
-                )
-
-        def __get__(self, instance, owner=None):
-            if instance is None:
-                return self
-            if self.attrname is None:
-                raise TypeError(
-                    "Cannot use cached_property instance without calling __set_name__ on it."
-                )
-            try:
-                cache = instance.__dict__
-            except AttributeError:  # not all objects have __dict__ (e.g. class defines slots)
-                msg = (
-                    f"No '__dict__' attribute on {type(instance).__name__!r} "
-                    f"instance to cache {self.attrname!r} property."
-                )
-                raise TypeError(msg) from None
-            val = cache.get(self.attrname, _NOT_FOUND)
-            if val is _NOT_FOUND:
-                with self.lock:
-                    # check if another thread filled cache while we awaited lock
-                    val = cache.get(self.attrname, _NOT_FOUND)
-                    if val is _NOT_FOUND:
-                        val = self.func(instance)
-                        try:
-                            cache[self.attrname] = val
-                        except TypeError:
-                            msg = (
-                                f"The '__dict__' attribute on {type(instance).__name__!r} instance "
-                                f"does not support item assignment for caching {self.attrname!r} property."
-                            )
-                            raise TypeError(msg) from None
-            return val
-
-        __class_getitem__ = classmethod(GenericAlias)
-
-else:
-    pass
-
-
 builtin_zip = zip
 if sys.version_info >= (3, 10):
     zip = builtin_zip

yt/data_objects/index_subobjects/octree_subset.py

@@ -1,5 +1,5 @@
-import sys
 from contextlib import contextmanager
+from functools import cached_property
 from itertools import product, repeat
 from typing import Tuple
 
@@ -21,11 +21,6 @@
 from yt.utilities.lib.geometry_utils import compute_morton
 from yt.utilities.logger import ytLogger as mylog
 
-if sys.version_info >= (3, 8):
-    from functools import cached_property
-else:
-    from yt._maintenance.backports import cached_property
-
 
 def cell_count_cache(func):
     def cc_cache_func(self, dobj):

yt/data_objects/region_expression.py

@@ -1,5 +1,5 @@
-import sys
 import weakref
+from functools import cached_property
 
 from yt.funcs import obj_length
 from yt.units.yt_array import YTQuantity
@@ -8,11 +8,6 @@
 
 from .data_containers import _get_ipython_key_completion
 
-if sys.version_info >= (3, 8):
-    from functools import cached_property
-else:
-    from yt._maintenance.backports import cached_property
-
 
 class RegionExpression:
     def __init__(self, ds):

yt/data_objects/static_output.py

@@ -9,6 +9,7 @@
 import warnings
 import weakref
 from collections import defaultdict
+from functools import cached_property
 from importlib.util import find_spec
 from stat import ST_CTIME
 from typing import DefaultDict, Dict, List, Optional, Set, Tuple, Type, Union
@@ -60,11 +61,6 @@
 from yt.utilities.parallel_tools.parallel_analysis_interface import parallel_root_only
 from yt.utilities.parameter_file_storage import NoParameterShelf, ParameterFileStore
 
-if sys.version_info >= (3, 8):
-    from functools import cached_property
-else:
-    from yt._maintenance.backports import cached_property
-
 if sys.version_info >= (3, 9):
     from collections.abc import MutableMapping
 else:

yt/fields/field_type_container.py

@@ -3,17 +3,12 @@
 """
 
 import inspect
-import sys
 import textwrap
 import weakref
+from functools import cached_property
 
 from yt.fields.derived_field import DerivedField
 
-if sys.version_info >= (3, 8):
-    from functools import cached_property
-else:
-    from yt._maintenance.backports import cached_property
-
 
 def _fill_values(values):
     value = (

yt/frontends/boxlib/data_structures.py

@@ -1,8 +1,8 @@
 import glob
 import os
 import re
-import sys
 from collections import namedtuple
+from functools import cached_property
 from stat import ST_CTIME
 from typing import Type
 
@@ -25,10 +25,6 @@
     WarpXFieldInfo,
 )
 
-if sys.version_info >= (3, 8):
-    from functools import cached_property
-else:
-    from yt._maintenance.backports import cached_property
 # This is what we use to find scientific notation that might include d's
 # instead of e's.
 _scinot_finder = re.compile(r"[-+]?[0-9]*\.?[0-9]+([eEdD][-+]?[0-9]+)?")

yt/frontends/enzo/data_structures.py

@@ -1,10 +1,10 @@
 import os
 import re
 import string
-import sys
 import time
 import weakref
 from collections import defaultdict
+from functools import cached_property
 
 import numpy as np
 from more_itertools import always_iterable
@@ -21,11 +21,6 @@
 
 from .fields import EnzoFieldInfo
 
-if sys.version_info >= (3, 8):
-    from functools import cached_property
-else:
-    from yt._maintenance.backports import cached_property
-
 
 class EnzoGrid(AMRGridPatch):
     """

yt/frontends/enzo_e/data_structures.py

@@ -1,5 +1,5 @@
 import os
-import sys
+from functools import cached_property
 
 import numpy as np
 
@@ -23,11 +23,6 @@
 from yt.utilities.logger import ytLogger as mylog
 from yt.utilities.on_demand_imports import _h5py as h5py, _libconf as libconf
 
-if sys.version_info >= (3, 8):
-    from functools import cached_property
-else:
-    from yt._maintenance.backports import cached_property
-
 
 class EnzoEGrid(AMRGridPatch):
     """