chore: drop Python 3.5 (#3719)

* chore: drop Python 3.5 support

* chore: more fstrings with flynt's help

* ci: drop Python 3.5

* chore: bump dependency versions

* docs: touch up py::args

* tests: remove deprecation warning

* Ban smartquotes

* Very minor tweaks (by-product of reviewing PR #3719).
Co-authored-by: Aaron Gokaslan <skylion.aaron@gmail.com>
Co-authored-by: Ralf W. Grosse-Kunstleve <rwgk@google.com>

noxfile.py

@@ -2,7 +2,7 @@ import nox
 
 nox.options.sessions = ["lint", "tests", "tests_packaging"]
 
-PYTHON_VERSIONS = ["3.5", "3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
+PYTHON_VERSIONS = ["3.6", "3.7", "3.8", "3.9", "3.10", "3.11"]
 
 
 @nox.session(reuse_venv=True)

pybind11/__init__.py

 import sys
 
-if sys.version_info < (3, 5):
-    msg = "pybind11 does not support Python < 3.5. 2.9 was the last release supporting older Pythons."
+if sys.version_info < (3, 6):
+    msg = "pybind11 does not support Python < 3.6. 2.9 was the last release supporting Python 2.7 and 3.5."
     raise ImportError(msg)
 
 

pybind11/setup_helpers.py

@@ -200,7 +200,7 @@ class Pybind11Extension(_Extension):  # type: ignore[misc]
             current_macos = tuple(int(x) for x in platform.mac_ver()[0].split(".")[:2])
             desired_macos = (10, 9) if level < 17 else (10, 14)
             macos_string = ".".join(str(x) for x in min(current_macos, desired_macos))
-            macosx_min = "-mmacosx-version-min={}".format(macos_string)
+            macosx_min = f"-mmacosx-version-min={macos_string}"
             cflags += [macosx_min]
             ldflags += [macosx_min]
 
@@ -322,9 +322,9 @@ def intree_extensions(
 
     if not exts:
         msg = (
-            "path {path} is not a child of any of the directories listed "
-            "in 'package_dir' ({package_dir})"
-        ).format(path=path, package_dir=package_dir)
+            f"path {path} is not a child of any of the directories listed "
+            f"in 'package_dir' ({package_dir})"
+        )
         raise ValueError(msg)
 
     return exts
@@ -419,7 +419,7 @@ class ParallelCompile:
         self.default = default
         self.max = max
         self.needs_recompile = needs_recompile
-        self._old = []  # type: List[CCompilerMethod]
+        self._old: List[CCompilerMethod] = []
 
     def function(self) -> CCompilerMethod:
         """

setup.cfg

@@ -14,7 +14,6 @@ classifiers =
     Topic :: Utilities
     Programming Language :: C++
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
@@ -38,7 +37,7 @@ project_urls =
     Chat = https://gitter.im/pybind/Lobby
 
 [options]
-python_requires = >=3.5
+python_requires = >=3.6
 zip_safe = False
 
 
@@ -46,14 +45,5 @@ zip_safe = False
 max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
-ignore =
-    # required for pretty matrix formatting: multiple spaces after `,` and `[`
-    E201, E241, W504,
-    # camelcase 'cPickle' imported as lowercase 'pickle'
-    N813
-    # Black conflict
-    W503, E203
-
-
-[tool:pytest]
-timeout = 300
+extend-ignore = E203, E722, B950
+select = C,E,F,N,W,B,B9

setup.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Setup script for PyPI; use CMakeFile.txt to build extension modules
 
@@ -41,12 +41,10 @@ def build_expected_version_hex(matches: Dict[str, str]) -> str:
                     serial = int(level_serial[len(level) :])
                     break
     if serial is None:
-        msg = 'Invalid PYBIND11_VERSION_PATCH: "{}"'.format(patch_level_serial)
+        msg = f'Invalid PYBIND11_VERSION_PATCH: "{patch_level_serial}"'
         raise RuntimeError(msg)
-    version_hex_str = "{:02x}{:02x}{:02x}{}{:x}".format(
-        major, minor, patch, level[:1], serial
-    )
-    return "0x{}".format(version_hex_str.upper())
+    version_hex_str = f"{major:02x}{minor:02x}{patch:02x}{level[:1]}{serial:x}"
+    return f"0x{version_hex_str.upper()}"
 
 
 # PYBIND11_GLOBAL_SDIST will build a different sdist, with the python-headers
@@ -66,7 +64,7 @@ to_src = (
 
 
 # Read the listed version
-loc = {}  # type: Dict[str, str]
+loc: Dict[str, str] = {}
 code = compile(VERSION_FILE.read_text(encoding="utf-8"), "pybind11/_version.py", "exec")
 exec(code, loc)
 version = loc["__version__"]
@@ -75,17 +73,13 @@ version = loc["__version__"]
 matches = dict(VERSION_REGEX.findall(COMMON_FILE.read_text(encoding="utf8")))
 cpp_version = "{MAJOR}.{MINOR}.{PATCH}".format(**matches)
 if version != cpp_version:
-    msg = "Python version {} does not match C++ version {}!".format(
-        version, cpp_version
-    )
+    msg = f"Python version {version} does not match C++ version {cpp_version}!"
     raise RuntimeError(msg)
 
 version_hex = matches.get("HEX", "MISSING")
 exp_version_hex = build_expected_version_hex(matches)
 if version_hex != exp_version_hex:
-    msg = "PYBIND11_VERSION_HEX {} does not match expected value {}!".format(
-        version_hex, exp_version_hex
-    )
+    msg = f"PYBIND11_VERSION_HEX {version_hex} does not match expected value {exp_version_hex}!"
     raise RuntimeError(msg)
 
 

tests/extra_python_package/test_files.py

@@ -145,9 +145,9 @@ def test_build_sdist(monkeypatch, tmpdir):
             contents = f.read().decode("utf8")
         assert 'set(pybind11_INCLUDE_DIR "${PACKAGE_PREFIX_DIR}/include")' in contents
 
-    files = {"pybind11/{}".format(n) for n in all_files}
+    files = {f"pybind11/{n}" for n in all_files}
     files |= sdist_files
-    files |= {"pybind11{}".format(n) for n in local_sdist_files}
+    files |= {f"pybind11{n}" for n in local_sdist_files}
     files.add("pybind11.egg-info/entry_points.txt")
     files.add("pybind11.egg-info/requires.txt")
     assert simpler == files
@@ -200,9 +200,9 @@ def test_build_global_dist(monkeypatch, tmpdir):
         ) as f:
             pyproject_toml = f.read()
 
-    files = {"pybind11/{}".format(n) for n in all_files}
+    files = {f"pybind11/{n}" for n in all_files}
     files |= sdist_files
-    files |= {"pybind11_global{}".format(n) for n in local_sdist_files}
+    files |= {f"pybind11_global{n}" for n in local_sdist_files}
     assert simpler == files
 
     with open(os.path.join(MAIN_DIR, "tools", "setup_global.py.in"), "rb") as f:
@@ -227,7 +227,7 @@ def tests_build_wheel(monkeypatch, tmpdir):
 
     (wheel,) = tmpdir.visit("*.whl")
 
-    files = {"pybind11/{}".format(n) for n in all_files}
+    files = {f"pybind11/{n}" for n in all_files}
     files |= {
         "dist-info/LICENSE",
         "dist-info/METADATA",
@@ -241,9 +241,7 @@ def tests_build_wheel(monkeypatch, tmpdir):
         names = z.namelist()
 
     trimmed = {n for n in names if "dist-info" not in n}
-    trimmed |= {
-        "dist-info/{}".format(n.split("/", 1)[-1]) for n in names if "dist-info" in n
-    }
+    trimmed |= {f"dist-info/{n.split('/', 1)[-1]}" for n in names if "dist-info" in n}
     assert files == trimmed
 
 
@@ -257,8 +255,8 @@ def tests_build_global_wheel(monkeypatch, tmpdir):
 
     (wheel,) = tmpdir.visit("*.whl")
 
-    files = {"data/data/{}".format(n) for n in src_files}
-    files |= {"data/headers/{}".format(n[8:]) for n in headers}
+    files = {f"data/data/{n}" for n in src_files}
+    files |= {f"data/headers/{n[8:]}" for n in headers}
     files |= {
         "dist-info/LICENSE",
         "dist-info/METADATA",

tests/extra_setuptools/test_setuphelper.py

@@ -18,7 +18,7 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
 
     (tmpdir / "setup.py").write_text(
         dedent(
-            """\
+            f"""\
             import sys
             sys.path.append({MAIN_DIR!r})
 
@@ -51,7 +51,7 @@ def test_simple_setup_py(monkeypatch, tmpdir, parallel, std):
                 ext_modules=ext_modules,
             )
             """
-        ).format(MAIN_DIR=MAIN_DIR, std=std, parallel=parallel),
+        ),
         encoding="ascii",
     )
 

tests/pytest.ini

 [pytest]
-minversion = 3.1
+minversion = 3.10
 norecursedirs = test_* extra_*
 xfail_strict = True
 addopts =
-    # show summary of skipped tests
-    -rs
+    # show summary of tests
+    -ra
     # capture only Python print and C++ py::print, but not C output (low-level Python errors)
     --capture=sys
+    # Show local info when a failure occurs
+    --showlocals
+log_cli_level = info
 filterwarnings =
     # make warnings into errors but ignore certain third-party extension issues
     error

tests/requirements.txt

-numpy==1.16.6; python_version<"3.6" and sys_platform!="win32" and platform_python_implementation!="PyPy"
-numpy==1.19.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.6"
-numpy==1.20.0; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
+numpy==1.21.5; platform_python_implementation=="PyPy" and sys_platform=="linux" and python_version=="3.7"
 numpy==1.19.3; platform_python_implementation!="PyPy" and python_version=="3.6"
-numpy==1.21.3; platform_python_implementation!="PyPy" and python_version>="3.7" and python_version<"3.11"
-py @ git+https://github.com/pytest-dev/py; python_version>="3.11"
-pytest==4.6.9; python_version<"3.5"
-pytest==6.1.2; python_version=="3.5"
-pytest==6.2.4; python_version>="3.6"
+numpy==1.21.5; platform_python_implementation!="PyPy" and python_version>="3.7" and python_version<"3.10"
+numpy==1.22.2; platform_python_implementation!="PyPy" and python_version>="3.10" and python_version<"3.11"
+pytest==7.0.0
 pytest-timeout
-scipy==1.2.3; platform_python_implementation!="PyPy" and python_version<"3.6"
-scipy==1.5.4; platform_python_implementation!="PyPy" and python_version>="3.6" and python_version<"3.10"
+scipy==1.5.4; platform_python_implementation!="PyPy" and python_version<"3.10"
+scipy==1.8.0; platform_python_implementation!="PyPy" and python_version=="3.10"

tests/test_builtin_casters.py

@@ -50,7 +50,7 @@ def test_single_char_arguments():
     """Tests failures for passing invalid inputs to char-accepting functions"""
 
     def toobig_message(r):
-        return "Character code point not in range({:#x})".format(r)
+        return f"Character code point not in range({r:#x})"
 
     toolong_message = "Expected a character, but multi-character string found"
 

tests/test_callbacks.py

@@ -17,7 +17,7 @@ def test_callbacks():
         return "func2", a, b, c, d
 
     def func3(a):
-        return "func3({})".format(a)
+        return f"func3({a})"
 
     assert m.test_callback1(func1) == "func1"
     assert m.test_callback2(func2) == ("func2", "Hello", "x", True, 5)
@@ -188,14 +188,8 @@ def test_callback_num_times():
         if not rep:
             print()
         print(
-            "callback_num_times: {:d} million / {:.3f} seconds = {:.3f} million / second".format(
-                num_millions, td, rate
-            )
+            f"callback_num_times: {num_millions:d} million / {td:.3f} seconds = {rate:.3f} million / second"
         )
     if len(rates) > 1:
         print("Min    Mean   Max")
-        print(
-            "{:6.3f} {:6.3f} {:6.3f}".format(
-                min(rates), sum(rates) / len(rates), max(rates)
-            )
-        )
+        print(f"{min(rates):6.3f} {sum(rates) / len(rates):6.3f} {max(rates):6.3f}")

tests/test_chrono.py

@@ -100,7 +100,7 @@ SKIP_TZ_ENV_ON_WIN = pytest.mark.skipif(
 )
 def test_chrono_system_clock_roundtrip_time(time1, tz, monkeypatch):
     if tz is not None:
-        monkeypatch.setenv("TZ", "/usr/share/zoneinfo/{}".format(tz))
+        monkeypatch.setenv("TZ", f"/usr/share/zoneinfo/{tz}")
 
     # Roundtrip the time
     datetime2 = m.test_chrono2(time1)

tests/test_cmake_build/test.py

@@ -5,4 +5,4 @@ import test_cmake_build
 assert isinstance(__file__, str)  # Test this is properly set
 
 assert test_cmake_build.add(1, 2) == 3
-print("{} imports, runs, and adds: 1 + 2 = 3".format(sys.argv[1]))
+print(f"{sys.argv[1]} imports, runs, and adds: 1 + 2 = 3")

tests/test_eigen.py

@@ -221,9 +221,7 @@ def test_nonunit_stride_to_python():
     assert np.all(m.diagonal(ref) == ref.diagonal())
     assert np.all(m.diagonal_1(ref) == ref.diagonal(1))
     for i in range(-5, 7):
-        assert np.all(
-            m.diagonal_n(ref, i) == ref.diagonal(i)
-        ), "m.diagonal_n({})".format(i)
+        assert np.all(m.diagonal_n(ref, i) == ref.diagonal(i)), f"m.diagonal_n({i})"
 
     assert np.all(m.block(ref, 2, 1, 3, 3) == ref[2:5, 1:4])
     assert np.all(m.block(ref, 1, 4, 4, 2) == ref[1:, 4:])
@@ -236,7 +234,7 @@ def test_eigen_ref_to_python():
         mymat = chol(np.array([[1.0, 2, 4], [2, 13, 23], [4, 23, 77]]))
         assert np.all(
             mymat == np.array([[1, 0, 0], [2, 3, 0], [4, 5, 6]])
-        ), "cholesky{}".format(i)
+        ), f"cholesky{i}"
 
 
 def assign_both(a1, a2, r, c, v):

tests/test_exceptions.py

@@ -88,7 +88,7 @@ def test_python_call_in_catch():
 def ignore_pytest_unraisable_warning(f):
     unraisable = "PytestUnraisableExceptionWarning"
     if hasattr(pytest, unraisable):  # Python >= 3.8 and pytest >= 6
-        dec = pytest.mark.filterwarnings("ignore::pytest.{}".format(unraisable))
+        dec = pytest.mark.filterwarnings(f"ignore::pytest.{unraisable}")
         return dec(f)
     else:
         return f

tests/test_numpy_array.py

@@ -18,9 +18,7 @@ def test_dtypes():
         assert check.numpy == check.pybind11, check
         if check.numpy.num != check.pybind11.num:
             print(
-                "NOTE: typenum mismatch for {}: {} != {}".format(
-                    check, check.numpy.num, check.pybind11.num
-                )
+                f"NOTE: typenum mismatch for {check}: {check.numpy.num} != {check.pybind11.num}"
             )
 
 
@@ -116,9 +114,7 @@ def test_at_fail(arr, dim):
     for func in m.at_t, m.mutate_at_t:
         with pytest.raises(IndexError) as excinfo:
             func(arr, *([0] * dim))
-        assert str(excinfo.value) == "index dimension mismatch: {} (ndim = 2)".format(
-            dim
-        )
+        assert str(excinfo.value) == f"index dimension mismatch: {dim} (ndim = 2)"
 
 
 def test_at(arr):
@@ -192,8 +188,6 @@ def test_make_empty_shaped_array():
 
 def test_wrap():
     def assert_references(a, b, base=None):
-        from distutils.version import LooseVersion
-
         if base is None:
             base = a
         assert a is not b
@@ -204,7 +198,8 @@ def test_wrap():
         assert a.flags.f_contiguous == b.flags.f_contiguous
         assert a.flags.writeable == b.flags.writeable
         assert a.flags.aligned == b.flags.aligned
-        if LooseVersion(np.__version__) >= LooseVersion("1.14.0"):
+        # 1.13 supported Python 3.6
+        if tuple(int(x) for x in np.__version__.split(".")[:2]) >= (1, 14):
             assert a.flags.writebackifcopy == b.flags.writebackifcopy
         else:
             assert a.flags.updateifcopy == b.flags.updateifcopy

tests/test_numpy_dtypes.py

@@ -14,7 +14,7 @@ def simple_dtype():
     return np.dtype(
         {
             "names": ["bool_", "uint_", "float_", "ldbl_"],
-            "formats": ["?", "u4", "f4", "f{}".format(ld.itemsize)],
+            "formats": ["?", "u4", "f4", f"f{ld.itemsize}"],
             "offsets": [0, 4, 8, (16 if ld.alignment > 4 else 12)],
         }
     )
@@ -125,7 +125,7 @@ def test_dtype(simple_dtype):
     assert [x.replace(" ", "") for x in m.print_dtypes()] == [
         simple_dtype_fmt(),
         packed_dtype_fmt(),
-        "[('a',{}),('b',{})]".format(simple_dtype_fmt(), packed_dtype_fmt()),
+        f"[('a',{simple_dtype_fmt()}),('b',{packed_dtype_fmt()})]",
         partial_dtype_fmt(),
         partial_nested_fmt(),
         "[('a','S3'),('b','S3')]",

tests/test_opaque_types.py

@@ -12,7 +12,7 @@ def test_string_list():
     assert lst.back() == "Element 2"
 
     for i, k in enumerate(lst, start=1):
-        assert k == "Element {}".format(i)
+        assert k == f"Element {i}"
     lst.pop_back()
     assert m.print_opaque_list(lst) == "Opaque list: [Element 1]"
 

tests/test_pytypes.py

@@ -305,8 +305,8 @@ def test_non_converting_constructors():
         for move in [True, False]:
             with pytest.raises(TypeError) as excinfo:
                 m.nonconverting_constructor(t, v, move)
-            expected_error = "Object of type '{}' is not an instance of '{}'".format(
-                type(v).__name__, t
+            expected_error = (
+                f"Object of type '{type(v).__name__}' is not an instance of '{t}'"
             )
             assert str(excinfo.value) == expected_error
 

tests/test_sequences_and_iterators.py

 import pytest
+from pytest import approx
 
 from pybind11_tests import ConstructorStats
 from pybind11_tests import sequences_and_iterators as m
 
 
-def isclose(a, b, rel_tol=1e-05, abs_tol=0.0):
-    """Like math.isclose() from Python 3.5"""
-    return abs(a - b) <= max(rel_tol * max(abs(a), abs(b)), abs_tol)
-
-
-def allclose(a_list, b_list, rel_tol=1e-05, abs_tol=0.0):
-    return all(
-        isclose(a, b, rel_tol=rel_tol, abs_tol=abs_tol) for a, b in zip(a_list, b_list)
-    )
-
-
 def test_slice_constructors():
     assert m.make_forward_slice_size_t() == slice(0, -1, 1)
     assert m.make_reversed_slice_object() == slice(None, None, -1)
@@ -117,7 +107,8 @@ def test_sequence():
     assert 12.34 not in s
     s[0], s[3] = 12.34, 56.78
     assert 12.34 in s
-    assert isclose(s[0], 12.34) and isclose(s[3], 56.78)
+    assert s[0] == approx(12.34, rel=1e-05)
+    assert s[3] == approx(56.78, rel=1e-05)
 
     rev = reversed(s)
     assert cstats.values() == ["of size", "5"]
@@ -132,14 +123,14 @@ def test_sequence():
     assert cstats.values() == ["of size", "0"]
 
     expected = [0, 56.78, 0, 0, 12.34]
-    assert allclose(rev, expected)
-    assert allclose(rev2, expected)
+    assert rev == approx(expected, rel=1e-05)
+    assert rev2 == approx(expected, rel=1e-05)
     assert rev == rev2
 
     rev[0::2] = m.Sequence([2.0, 2.0, 2.0])
     assert cstats.values() == ["of size", "3", "from std::vector"]
 
-    assert allclose(rev, [2, 56.78, 2, 0, 2])
+    assert rev == approx([2, 56.78, 2, 0, 2], rel=1e-05)
 
     assert cstats.alive() == 4
     del it