feat: remove Python 3.6 support (#5177)

* Change Python version guard: PYTHON < 3.7 IS UNSUPPORTED.

* Replace or remove Python 3.6 jobs.

* Move appveyor to Python 3.8

* Change `[tool.pylint]` `master.py-version` from `3.6` to `3.8`

* Change `[tool.pylint]` `master.py-version` to `3.7`

* Remove `centos:7` job; Change almalinux:8 job to use Python 3.8

* Try 🐍 3.8 • ubuntu-20.04 • x64 without `-DCMAKE_CXX_FLAGS="-D_=1"`

* Update setup.cfg as suggested by @henryiii

* Try running `cmake --build . --target cpptest` on all platforms (`standard` job).

* Disable deadsnakes jobs entirely.

* Apply PR #5179: Add Python 3.10, 3.11, 3.12 to win32 job matrix.

* Add back `-DCMAKE_CXX_FLAGS="-D_=1"` but do not install boost in that case.

* PY_VERSION_HEX < 3.7 cleanup pass: include/pybind11

* WITH_THREAD cleanup pass: include/pybind11

* Undo incorrect change.

* Revert "Disable deadsnakes jobs entirely."

This reverts commit bbcd0087b2.

* WITH_THREAD cleanup pass: tests/

* Change Python version guard in pybind11/__init__.py: pybind11 does not support Python < 3.7.

* Misc cleanup pass

* chore: use future imports

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update tests/test_numpy_array.py

* Update test_numpy_array.py

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>

.appveyor.yml

@@ -9,7 +9,7 @@ platform:
 - x86
 environment:
   matrix:
-  - PYTHON: 36
+  - PYTHON: 38
     CONFIG: Debug
 install:
 - ps: |

.github/workflows/ci.yml

@@ -32,7 +32,7 @@ jobs:
       matrix:
         runs-on: [ubuntu-20.04, windows-2022, macos-13]
         python:
-        - '3.6'
+        - '3.8'
         - '3.9'
         - '3.12'
         - '3.13'
@@ -48,16 +48,17 @@ jobs:
         include:
           # Just add a key
           - runs-on: ubuntu-20.04
-            python: '3.6'
+            python: '3.8'
             args: >
               -DPYBIND11_FINDPYTHON=ON
               -DCMAKE_CXX_FLAGS="-D_=1"
+            exercise_D_: 1
           - runs-on: ubuntu-20.04
             python: 'pypy-3.8'
             args: >
               -DPYBIND11_FINDPYTHON=ON
           - runs-on: windows-2019
-            python: '3.6'
+            python: '3.8'
             args: >
               -DPYBIND11_FINDPYTHON=ON
           # Inject a couple Windows 2019 runs
@@ -82,7 +83,7 @@ jobs:
 
     - name: Setup Boost (Linux)
       # Can't use boost + define _
-      if: runner.os == 'Linux' && matrix.python != '3.6'
+      if: runner.os == 'Linux' && matrix.exercise_D_ != 1
       run: sudo apt-get install libboost-dev
 
     - name: Setup Boost (macOS)
@@ -655,15 +656,13 @@ jobs:
         cmake --build build-17 --target test_cmake_build
 
 
-  # Testing on CentOS (manylinux uses a centos base, and this is an easy way
-  # to get GCC 4.8, which is the manylinux1 compiler).
+  # Testing on CentOS (manylinux uses a centos base).
   centos:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
         container:
-          - "centos:7"  # GCC 4.8
           - "almalinux:8"
           - "almalinux:9"
 
@@ -673,18 +672,13 @@ jobs:
     steps:
     - name: Latest actions/checkout
       uses: actions/checkout@v4
-      if: matrix.container != 'centos:7'
 
-    - name: Pin actions/checkout as required for centos:7
-      uses: actions/checkout@v3
-      if: matrix.container == 'centos:7'
+    - name: Add Python 3.8
+      if: matrix.container == 'almalinux:8'
+      run: dnf update -y && dnf install -y python38-devel gcc-c++ make git
 
-    - name: Add Python 3 (RHEL 7)
-      if: matrix.container == 'centos:7'
-      run: yum update -y && yum install -y python3-devel gcc-c++ make git
-
-    - name: Add Python 3 (RHEL 8+)
-      if: matrix.container != 'centos:7'
+    - name: Add Python 3 (default)
+      if: matrix.container != 'almalinux:8'
       run: dnf update -y && dnf install -y python3-devel gcc-c++ make git
 
     - name: Update pip
@@ -807,7 +801,6 @@ jobs:
       fail-fast: false
       matrix:
         python:
-        - '3.6'
         - '3.7'
         - '3.8'
         - '3.9'

.github/workflows/pip.yml

@@ -21,19 +21,18 @@ env:
 
 jobs:
   # This builds the sdists and wheels and makes sure the files are exactly as
-  # expected. Using Windows and Python 3.6, since that is often the most
-  # challenging matrix element.
+  # expected.
   test-packaging:
-    name: 🐍 3.6 • 📦 tests • windows-latest
+    name: 🐍 3.8 • 📦 tests • windows-latest
     runs-on: windows-latest
 
     steps:
     - uses: actions/checkout@v4
 
-    - name: Setup 🐍 3.6
+    - name: Setup 🐍 3.8
       uses: actions/setup-python@v5
       with:
-        python-version: 3.6
+        python-version: 3.8
 
     - name: Prepare env
       run: |

README.rst

@@ -34,7 +34,7 @@ dependency.
 Think of this library as a tiny self-contained version of Boost.Python
 with everything stripped away that isn't relevant for binding
 generation. Without comments, the core header files only require ~4K
-lines of code and depend on Python (3.6+, or PyPy) and the C++
+lines of code and depend on Python (3.7+, or PyPy) and the C++
 standard library. This compact implementation was possible thanks to
 some C++11 language features (specifically: tuples, lambda functions and
 variadic templates). Since its creation, this library has grown beyond
@@ -79,7 +79,7 @@ Goodies
 In addition to the core functionality, pybind11 provides some extra
 goodies:
 
-- Python 3.6+, and PyPy3 7.3 are supported with an implementation-agnostic
+- Python 3.7+, and PyPy3 7.3 are supported with an implementation-agnostic
   interface (pybind11 2.9 was the last version to support Python 2 and 3.5).
 
 - It is possible to bind C++11 lambda functions with captured

docs/benchmark.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import datetime as dt
 import os
 import random

docs/compiling.rst

@@ -426,7 +426,7 @@ with ``PYTHON_EXECUTABLE``.  For example:
 
 .. code-block:: bash
 
-    cmake -DPYBIND11_PYTHON_VERSION=3.6 ..
+    cmake -DPYBIND11_PYTHON_VERSION=3.7 ..
 
     # Another method:
     cmake -DPYTHON_EXECUTABLE=/path/to/python ..
@@ -493,7 +493,7 @@ existing targets instead:
     cmake_minimum_required(VERSION 3.15...3.22)
     project(example LANGUAGES CXX)
 
-    find_package(Python 3.6 COMPONENTS Interpreter Development REQUIRED)
+    find_package(Python 3.7 COMPONENTS Interpreter Development REQUIRED)
     find_package(pybind11 CONFIG REQUIRED)
     # or add_subdirectory(pybind11)
 

docs/conf.py

@@ -11,6 +11,7 @@
 #
 # All configuration values have a default; values that are commented out
 # serve to show the default.
+from __future__ import annotations
 
 import os
 import re

include/pybind11/detail/class.h

@@ -567,16 +567,8 @@ inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
     type->tp_traverse = pybind11_traverse;
     type->tp_clear = pybind11_clear;
 
-    static PyGetSetDef getset[] = {{
-#if PY_VERSION_HEX < 0x03070000
-                                       const_cast<char *>("__dict__"),
-#else
-                                       "__dict__",
-#endif
-                                       PyObject_GenericGetDict,
-                                       PyObject_GenericSetDict,
-                                       nullptr,
-                                       nullptr},
+    static PyGetSetDef getset[]
+        = {{"__dict__", PyObject_GenericGetDict, PyObject_GenericSetDict, nullptr, nullptr},
            {nullptr, nullptr, nullptr, nullptr, nullptr}};
     type->tp_getset = getset;
 }

include/pybind11/detail/common.h

@@ -272,9 +272,8 @@ PYBIND11_WARNING_DISABLE_MSVC(4505)
 #endif
 
 #include <Python.h>
-// Reminder: WITH_THREAD is always defined if PY_VERSION_HEX >= 0x03070000
-#if PY_VERSION_HEX < 0x03060000
-#    error "PYTHON < 3.6 IS UNSUPPORTED. pybind11 v2.9 was the last to support Python 2 and 3.5."
+#if PY_VERSION_HEX < 0x03070000
+#    error "PYTHON < 3.7 IS UNSUPPORTED. pybind11 v2.12 was the last to support Python 3.6."
 #endif
 #include <frameobject.h>
 #include <pythread.h>

include/pybind11/detail/internals.h

@@ -11,7 +11,7 @@
 
 #include "common.h"
 
-#if defined(WITH_THREAD) && defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+#if defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
 #    include "../gil.h"
 #endif
 
@@ -64,10 +64,9 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 
 // The old Python Thread Local Storage (TLS) API is deprecated in Python 3.7 in favor of the new
 // Thread Specific Storage (TSS) API.
-#if PY_VERSION_HEX >= 0x03070000
 // Avoid unnecessary allocation of `Py_tss_t`, since we cannot use
 // `Py_LIMITED_API` anyway.
-#    if PYBIND11_INTERNALS_VERSION > 4
+#if PYBIND11_INTERNALS_VERSION > 4
 #    define PYBIND11_TLS_KEY_REF Py_tss_t &
 #    if defined(__clang__)
 #        define PYBIND11_TLS_KEY_INIT(var)                                                        \
@@ -91,7 +90,7 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 #    define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_tss_set(&(key), (value))
 #    define PYBIND11_TLS_DELETE_VALUE(key) PyThread_tss_set(&(key), nullptr)
 #    define PYBIND11_TLS_FREE(key) PyThread_tss_delete(&(key))
-#    else
+#else
 #    define PYBIND11_TLS_KEY_REF Py_tss_t *
 #    define PYBIND11_TLS_KEY_INIT(var) Py_tss_t *var = nullptr;
 #    define PYBIND11_TLS_KEY_CREATE(var)                                                          \
@@ -100,29 +99,6 @@ inline PyObject *make_object_base_type(PyTypeObject *metaclass);
 #    define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_tss_set((key), (value))
 #    define PYBIND11_TLS_DELETE_VALUE(key) PyThread_tss_set((key), nullptr)
 #    define PYBIND11_TLS_FREE(key) PyThread_tss_free(key)
-#    endif
-#else
-// Usually an int but a long on Cygwin64 with Python 3.x
-#    define PYBIND11_TLS_KEY_REF decltype(PyThread_create_key())
-#    define PYBIND11_TLS_KEY_INIT(var) PYBIND11_TLS_KEY_REF var = 0;
-#    define PYBIND11_TLS_KEY_CREATE(var) (((var) = PyThread_create_key()) != -1)
-#    define PYBIND11_TLS_GET_VALUE(key) PyThread_get_key_value((key))
-#    if defined(PYPY_VERSION)
-// On CPython < 3.4 and on PyPy, `PyThread_set_key_value` strangely does not set
-// the value if it has already been set.  Instead, it must first be deleted and
-// then set again.
-inline void tls_replace_value(PYBIND11_TLS_KEY_REF key, void *value) {
-    PyThread_delete_key_value(key);
-    PyThread_set_key_value(key, value);
-}
-#        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_delete_key_value(key)
-#        define PYBIND11_TLS_REPLACE_VALUE(key, value)                                            \
-            ::pybind11::detail::tls_replace_value((key), (value))
-#    else
-#        define PYBIND11_TLS_DELETE_VALUE(key) PyThread_set_key_value((key), nullptr)
-#        define PYBIND11_TLS_REPLACE_VALUE(key, value) PyThread_set_key_value((key), (value))
-#    endif
-#    define PYBIND11_TLS_FREE(key) (void) key
 #endif
 
 // Python loads modules by default with dlopen with the RTLD_LOCAL flag; under libc++ and possibly
@@ -216,28 +192,27 @@ struct internals {
     PyTypeObject *static_property_type;
     PyTypeObject *default_metaclass;
     PyObject *instance_base;
-#if defined(WITH_THREAD)
     // Unused if PYBIND11_SIMPLE_GIL_MANAGEMENT is defined:
     PYBIND11_TLS_KEY_INIT(tstate)
-#    if PYBIND11_INTERNALS_VERSION > 4
+#if PYBIND11_INTERNALS_VERSION > 4
     PYBIND11_TLS_KEY_INIT(loader_life_support_tls_key)
-#    endif // PYBIND11_INTERNALS_VERSION > 4
+#endif // PYBIND11_INTERNALS_VERSION > 4
     // Unused if PYBIND11_SIMPLE_GIL_MANAGEMENT is defined:
     PyInterpreterState *istate = nullptr;
 
-#    if PYBIND11_INTERNALS_VERSION > 4
+#if PYBIND11_INTERNALS_VERSION > 4
     // Note that we have to use a std::string to allocate memory to ensure a unique address
     // We want unique addresses since we use pointer equality to compare function records
     std::string function_record_capsule_name = internals_function_record_capsule_name;
-#    endif
+#endif
 
     internals() = default;
     internals(const internals &other) = delete;
     internals &operator=(const internals &other) = delete;
     ~internals() {
-#    if PYBIND11_INTERNALS_VERSION > 4
+#if PYBIND11_INTERNALS_VERSION > 4
         PYBIND11_TLS_FREE(loader_life_support_tls_key);
-#    endif // PYBIND11_INTERNALS_VERSION > 4
+#endif // PYBIND11_INTERNALS_VERSION > 4
 
         // This destructor is called *after* Py_Finalize() in finalize_interpreter().
         // That *SHOULD BE* fine. The following details what happens when PyThread_tss_free is
@@ -248,7 +223,6 @@ struct internals {
         // that the `tstate` be allocated with the CPython allocator.
         PYBIND11_TLS_FREE(tstate);
     }
-#endif
 };
 
 /// Additional type information which does not fit into the PyTypeObject.
@@ -333,11 +307,7 @@ struct type_info {
 #endif
 
 #ifndef PYBIND11_INTERNALS_KIND
-#    if defined(WITH_THREAD)
 #    define PYBIND11_INTERNALS_KIND ""
-#    else
-#        define PYBIND11_INTERNALS_KIND "_without_thread"
-#    endif
 #endif
 
 #define PYBIND11_INTERNALS_ID                                                                     \
@@ -520,10 +490,9 @@ PYBIND11_NOINLINE internals &get_internals() {
         return **internals_pp;
     }
 
-#if defined(WITH_THREAD)
-#    if defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+#if defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
     gil_scoped_acquire gil;
-#    else
+#else
     // Ensure that the GIL is held since we will need to make Python calls.
     // Cannot use py::gil_scoped_acquire here since that constructor calls get_internals.
     struct gil_scoped_acquire_local {
@@ -533,7 +502,6 @@ PYBIND11_NOINLINE internals &get_internals() {
         ~gil_scoped_acquire_local() { PyGILState_Release(state); }
         const PyGILState_STATE state;
     } gil;
-#    endif
 #endif
     error_scope err_scope;
 
@@ -558,7 +526,6 @@ PYBIND11_NOINLINE internals &get_internals() {
         }
         auto *&internals_ptr = *internals_pp;
         internals_ptr = new internals();
-#if defined(WITH_THREAD)
 
         PyThreadState *tstate = PyThreadState_Get();
         // NOLINTNEXTLINE(bugprone-assignment-in-if-condition)
@@ -567,15 +534,14 @@ PYBIND11_NOINLINE internals &get_internals() {
         }
         PYBIND11_TLS_REPLACE_VALUE(internals_ptr->tstate, tstate);
 
-#    if PYBIND11_INTERNALS_VERSION > 4
+#if PYBIND11_INTERNALS_VERSION > 4
         // NOLINTNEXTLINE(bugprone-assignment-in-if-condition)
         if (!PYBIND11_TLS_KEY_CREATE(internals_ptr->loader_life_support_tls_key)) {
             pybind11_fail("get_internals: could not successfully initialize the "
                           "loader_life_support TSS key!");
         }
-#    endif
-        internals_ptr->istate = tstate->interp;
 #endif
+        internals_ptr->istate = tstate->interp;
         state_dict[PYBIND11_INTERNALS_ID] = capsule(internals_pp);
         internals_ptr->registered_exception_translators.push_front(&translate_exception);
         internals_ptr->static_property_type = make_static_property_type();
@@ -604,7 +570,7 @@ PYBIND11_NOINLINE internals &get_internals() {
 struct local_internals {
     type_map<type_info *> registered_types_cpp;
     std::forward_list<ExceptionTranslator> registered_exception_translators;
-#if defined(WITH_THREAD) && PYBIND11_INTERNALS_VERSION == 4
+#if PYBIND11_INTERNALS_VERSION == 4
 
     // For ABI compatibility, we can't store the loader_life_support TLS key in
     // the `internals` struct directly.  Instead, we store it in `shared_data` and
@@ -637,7 +603,7 @@ struct local_internals {
         loader_life_support_tls_key
             = static_cast<shared_loader_life_support_data *>(ptr)->loader_life_support_tls_key;
     }
-#endif //  defined(WITH_THREAD) && PYBIND11_INTERNALS_VERSION == 4
+#endif //  PYBIND11_INTERNALS_VERSION == 4
 };
 
 /// Works like `get_internals`, but for things which are locally registered.

include/pybind11/detail/type_caster_base.h

@@ -36,14 +36,13 @@ private:
     loader_life_support *parent = nullptr;
     std::unordered_set<PyObject *> keep_alive;
 
-#if defined(WITH_THREAD)
     // Store stack pointer in thread-local storage.
     static PYBIND11_TLS_KEY_REF get_stack_tls_key() {
-#    if PYBIND11_INTERNALS_VERSION == 4
+#if PYBIND11_INTERNALS_VERSION == 4
         return get_local_internals().loader_life_support_tls_key;
-#    else
+#else
         return get_internals().loader_life_support_tls_key;
-#    endif
+#endif
     }
     static loader_life_support *get_stack_top() {
         return static_cast<loader_life_support *>(PYBIND11_TLS_GET_VALUE(get_stack_tls_key()));
@@ -51,15 +50,6 @@ private:
     static void set_stack_top(loader_life_support *value) {
         PYBIND11_TLS_REPLACE_VALUE(get_stack_tls_key(), value);
     }
-#else
-    // Use single global variable for stack.
-    static loader_life_support **get_stack_pp() {
-        static loader_life_support *global_stack = nullptr;
-        return global_stack;
-    }
-    static loader_life_support *get_stack_top() { return *get_stack_pp(); }
-    static void set_stack_top(loader_life_support *value) { *get_stack_pp() = value; }
-#endif
 
 public:
     /// A new patient frame is created when a function is entered

include/pybind11/embed.h

@@ -103,9 +103,6 @@ inline void initialize_interpreter_pre_pyconfig(bool init_signal_handlers,
                                                 bool add_program_dir_to_path) {
     detail::precheck_interpreter();
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
-#    if defined(WITH_THREAD) && PY_VERSION_HEX < 0x03070000
-    PyEval_InitThreads();
-#    endif
 
     // Before it was special-cased in python 3.8, passing an empty or null argv
     // caused a segfault, so we have to reimplement the special case ourselves.

include/pybind11/gil.h

@@ -13,7 +13,7 @@
 
 #include <cassert>
 
-#if defined(WITH_THREAD) && !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+#if !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
 #    include "detail/internals.h"
 #endif
 
@@ -26,9 +26,7 @@ PyThreadState *get_thread_state_unchecked();
 
 PYBIND11_NAMESPACE_END(detail)
 
-#if defined(WITH_THREAD)
-
-#    if !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
+#if !defined(PYBIND11_SIMPLE_GIL_MANAGEMENT)
 
 /* The functions below essentially reproduce the PyGILState_* API using a RAII
  * pattern, but there are a few important differences:
@@ -188,7 +186,7 @@ private:
     bool active = true;
 };
 
-#    else // PYBIND11_SIMPLE_GIL_MANAGEMENT
+#else // PYBIND11_SIMPLE_GIL_MANAGEMENT
 
 class gil_scoped_acquire {
     PyGILState_STATE state;
@@ -216,32 +214,6 @@ public:
     void disarm() {}
 };
 
-#    endif // PYBIND11_SIMPLE_GIL_MANAGEMENT
-
-#else // WITH_THREAD
-
-class gil_scoped_acquire {
-public:
-    gil_scoped_acquire() {
-        // Trick to suppress `unused variable` error messages (at call sites).
-        (void) (this != (this + 1));
-    }
-    gil_scoped_acquire(const gil_scoped_acquire &) = delete;
-    gil_scoped_acquire &operator=(const gil_scoped_acquire &) = delete;
-    void disarm() {}
-};
-
-class gil_scoped_release {
-public:
-    gil_scoped_release() {
-        // Trick to suppress `unused variable` error messages (at call sites).
-        (void) (this != (this + 1));
-    }
-    gil_scoped_release(const gil_scoped_release &) = delete;
-    gil_scoped_release &operator=(const gil_scoped_release &) = delete;
-    void disarm() {}
-};
-
-#endif // WITH_THREAD
+#endif // PYBIND11_SIMPLE_GIL_MANAGEMENT
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

include/pybind11/stl/filesystem.h

@@ -14,8 +14,7 @@
 
 #ifdef __has_include
 #    if defined(PYBIND11_CPP17)
-#        if __has_include(<filesystem>) && \
-          PY_VERSION_HEX >= 0x03060000
+#        if __has_include(<filesystem>)
 #            include <filesystem>
 #            define PYBIND11_HAS_FILESYSTEM 1
 #        elif __has_include(<experimental/filesystem>)

noxfile.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import argparse
 
 import nox

pybind11/__init__.py

@@ -1,7 +1,9 @@
+from __future__ import annotations
+
 import sys
 
-if sys.version_info < (3, 6):  # noqa: UP036
-    msg = "pybind11 does not support Python < 3.6. 2.9 was the last release supporting Python 2.7 and 3.5."
+if sys.version_info < (3, 7):  # noqa: UP036
+    msg = "pybind11 does not support Python < 3.7. v2.12 was the last release supporting Python 3.6."
     raise ImportError(msg)
 
 

pybind11/__main__.py

@@ -1,4 +1,5 @@
 # pylint: disable=missing-function-docstring
+from __future__ import annotations
 
 import argparse
 import sys

pybind11/_version.py

@@ -1,7 +1,7 @@
-from typing import Union
+from __future__ import annotations
 
 
-def _to_int(s: str) -> Union[int, str]:
+def _to_int(s: str) -> int | str:
     try:
         return int(s)
     except ValueError:

pybind11/commands.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 
 DIR = os.path.abspath(os.path.dirname(__file__))

pybind11/setup_helpers.py

@@ -36,6 +36,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 # If you copy this file in, you don't
 # need the .pyi file; it's just an interface file for static type checkers.
+from __future__ import annotations
 
 import contextlib
 import os
@@ -52,7 +53,6 @@ from pathlib import Path
 from typing import (
     Any,
     Callable,
-    Dict,
     Iterable,
     Iterator,
     List,
@@ -113,10 +113,10 @@ class Pybind11Extension(_Extension):
     # flags are prepended, so that they can be further overridden, e.g. by
     # ``extra_compile_args=["-g"]``.
 
-    def _add_cflags(self, flags: List[str]) -> None:
+    def _add_cflags(self, flags: list[str]) -> None:
         self.extra_compile_args[:0] = flags
 
-    def _add_ldflags(self, flags: List[str]) -> None:
+    def _add_ldflags(self, flags: list[str]) -> None:
         self.extra_link_args[:0] = flags
 
     def __init__(self, *args: Any, **kwargs: Any) -> None:
@@ -250,7 +250,7 @@ cpp_flag_cache = None
 
 
 @lru_cache()
-def auto_cpp_level(compiler: Any) -> Union[str, int]:
+def auto_cpp_level(compiler: Any) -> str | int:
     """
     Return the max supported C++ std level (17, 14, or 11). Returns latest on Windows.
     """
@@ -288,8 +288,8 @@ class build_ext(_build_ext):  # noqa: N801
 
 
 def intree_extensions(
-    paths: Iterable[str], package_dir: Optional[Dict[str, str]] = None
-) -> List[Pybind11Extension]:
+    paths: Iterable[str], package_dir: dict[str, str] | None = None
+) -> list[Pybind11Extension]:
     """
     Generate Pybind11Extensions from source files directly located in a Python
     source tree.
@@ -409,7 +409,7 @@ class ParallelCompile:
 
     def __init__(
         self,
-        envvar: Optional[str] = None,
+        envvar: str | None = None,
         default: int = 0,
         max: int = 0,  # pylint: disable=redefined-builtin
         needs_recompile: Callable[[str, str], bool] = no_recompile,
@@ -418,7 +418,7 @@ class ParallelCompile:
         self.default = default
         self.max = max
         self.needs_recompile = needs_recompile
-        self._old: List[CCompilerMethod] = []
+        self._old: list[CCompilerMethod] = []
 
     def function(self) -> CCompilerMethod:
         """
@@ -427,14 +427,14 @@ class ParallelCompile:
 
         def compile_function(
             compiler: distutils.ccompiler.CCompiler,
-            sources: List[str],
-            output_dir: Optional[str] = None,
-            macros: Optional[List[Union[Tuple[str], Tuple[str, Optional[str]]]]] = None,
-            include_dirs: Optional[List[str]] = None,
+            sources: list[str],
+            output_dir: str | None = None,
+            macros: list[tuple[str] | tuple[str, str | None]] | None = None,
+            include_dirs: list[str] | None = None,
             debug: bool = False,
-            extra_preargs: Optional[List[str]] = None,
-            extra_postargs: Optional[List[str]] = None,
-            depends: Optional[List[str]] = None,
+            extra_preargs: list[str] | None = None,
+            extra_postargs: list[str] | None = None,
+            depends: list[str] | None = None,
         ) -> Any:
             # These lines are directly from distutils.ccompiler.CCompiler
             macros, objects, extra_postargs, pp_opts, build = compiler._setup_compile(  # type: ignore[attr-defined]

pyproject.toml

@@ -30,7 +30,7 @@ ignore_missing_imports = true
 
 
 [tool.pylint]
-master.py-version = "3.6"
+master.py-version = "3.7"
 reports.output-format = "colorized"
 messages_control.disable = [
   "design",
@@ -76,6 +76,8 @@ ignore = [
 ]
 unfixable = ["T20"]
 isort.known-first-party = ["env", "pybind11_cross_module_tests", "pybind11_tests"]
+isort.required-imports = ["from __future__ import annotations"]
+
 
 [tool.ruff.lint.per-file-ignores]
 "tests/**" = ["EM", "N", "E721"]

setup.cfg

@@ -14,7 +14,6 @@ classifiers =
     Topic :: Utilities
     Programming Language :: C++
     Programming Language :: Python :: 3 :: Only
-    Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
@@ -39,5 +38,5 @@ project_urls =
     Chat = https://gitter.im/pybind/Lobby
 
 [options]
-python_requires = >=3.6
+python_requires = >=3.7
 zip_safe = False

setup.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 
 # Setup script for PyPI; use CMakeFile.txt to build extension modules
+from __future__ import annotations
 
 import contextlib
 import os
@@ -9,9 +10,9 @@ import shutil
 import string
 import subprocess
 import sys
+from collections.abc import Generator
 from pathlib import Path
 from tempfile import TemporaryDirectory
-from typing import Dict, Iterator, List, Union
 
 import setuptools.command.sdist
 
@@ -23,7 +24,7 @@ VERSION_FILE = Path("pybind11/_version.py")
 COMMON_FILE = Path("include/pybind11/detail/common.h")
 
 
-def build_expected_version_hex(matches: Dict[str, str]) -> str:
+def build_expected_version_hex(matches: dict[str, str]) -> str:
     patch_level_serial = matches["PATCH"]
     serial = None
     major = int(matches["MAJOR"])
@@ -64,7 +65,7 @@ to_src = (
 
 
 # Read the listed version
-loc: 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__"]
@@ -84,9 +85,7 @@ if version_hex != exp_version_hex:
 
 
 # TODO: use literals & overload (typing extensions or Python 3.8)
-def get_and_replace(
-    filename: Path, binary: bool = False, **opts: str
-) -> Union[bytes, str]:
+def get_and_replace(filename: Path, binary: bool = False, **opts: str) -> bytes | str:
     if binary:
         contents = filename.read_bytes()
         return string.Template(contents.decode()).substitute(opts).encode()
@@ -97,7 +96,7 @@ def get_and_replace(
 # Use our input files instead when making the SDist (and anything that depends
 # on it, like a wheel)
 class SDist(setuptools.command.sdist.sdist):
-    def make_release_tree(self, base_dir: str, files: List[str]) -> None:
+    def make_release_tree(self, base_dir: str, files: list[str]) -> None:
         super().make_release_tree(base_dir, files)
 
         for to, src in to_src:
@@ -112,7 +111,7 @@ class SDist(setuptools.command.sdist.sdist):
 
 # Remove the CMake install directory when done
 @contextlib.contextmanager
-def remove_output(*sources: str) -> Iterator[None]:
+def remove_output(*sources: str) -> Generator[None, None, None]:
     try:
         yield
     finally:

tests/conftest.py

@@ -4,6 +4,8 @@ Extends output capture as needed by pybind11: ignore constructors, optional unor
 Adds docstring and exceptions message sanitizers.
 """
 
+from __future__ import annotations
+
 import contextlib
 import difflib
 import gc

tests/env.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import platform
 import sys
 import sysconfig

tests/extra_python_package/test_files.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import contextlib
 import os
 import string

tests/extra_setuptools/test_setuphelper.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 import subprocess
 import sys

tests/requirements.txt

@@ -1,10 +1,8 @@
 --only-binary=:all:
-build~=0.9; python_version=="3.6"
 build~=1.0; python_version>="3.7"
 numpy~=1.20.0; python_version=="3.7" and platform_python_implementation=="PyPy"
 numpy~=1.23.0; python_version=="3.8" and platform_python_implementation=="PyPy"
 numpy~=1.25.0; python_version=="3.9" and platform_python_implementation=='PyPy'
-numpy~=1.19.3; platform_python_implementation!="PyPy" and 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"
 numpy~=1.26.0; platform_python_implementation!="PyPy" and python_version>="3.11" and python_version<"3.13"

tests/test_async.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 asyncio = pytest.importorskip("asyncio")

tests/test_buffers.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import ctypes
 import io
 import struct

tests/test_builtin_casters.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 import pytest

tests/test_call_policies.cpp

@@ -95,7 +95,7 @@ TEST_SUBMODULE(call_policies, m) {
         },
         py::call_guard<DependentGuard, CustomGuard>());
 
-#if defined(WITH_THREAD) && !defined(PYPY_VERSION)
+#if !defined(PYPY_VERSION)
     // `py::call_guard<py::gil_scoped_release>()` should work in PyPy as well,
     // but it's unclear how to test it without `PyGILState_GetThisThreadState`.
     auto report_gil_status = []() {

tests/test_call_policies.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 import env  # noqa: F401

tests/test_callbacks.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import time
 from threading import Thread
 

tests/test_chrono.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import datetime
 
 import pytest

tests/test_class.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from unittest import mock
 
 import pytest

tests/test_cmake_build/test.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 import test_cmake_build

tests/test_const_name.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import const_name as m

tests/test_constants_and_functions.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 m = pytest.importorskip("pybind11_tests.constants_and_functions")

tests/test_copy_move.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import copy_move_policies as m

tests/test_custom_type_casters.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import custom_type_casters as m

tests/test_custom_type_setup.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import gc
 import weakref
 

tests/test_docstring_options.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pybind11_tests import docstring_options as m
 
 

tests/test_eigen_matrix.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import ConstructorStats

tests/test_eigen_tensor.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 import pytest

tests/test_embed/test_interpreter.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 from widget_module import Widget

tests/test_embed/test_trampoline.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import trampoline_module
 
 

tests/test_enum.py

@@ -1,4 +1,5 @@
 # ruff: noqa: SIM201 SIM300 SIM202
+from __future__ import annotations
 
 import pytest
 

tests/test_eval.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 
 import pytest

tests/test_eval_call.py

@@ -1,4 +1,5 @@
 # This file is called from 'test_eval.py'
+from __future__ import annotations
 
 if "call_test2" in locals():
     call_test2(y)  # noqa: F821 undefined name

tests/test_exceptions.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 import pytest

tests/test_factory_constructors.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import re
 
 import pytest

tests/test_gil_scoped.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import multiprocessing
 import sys
 import threading

tests/test_iostream.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from contextlib import redirect_stderr, redirect_stdout
 from io import StringIO
 

tests/test_kwargs_and_defaults.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import kwargs_and_defaults as m

tests/test_local_bindings.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 import env  # noqa: F401

tests/test_methods_and_attributes.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 import pytest

tests/test_modules.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import builtins
 
 import pytest

tests/test_multiple_inheritance.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 import env  # noqa: F401

tests/test_numpy_array.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 import env  # noqa: F401
@@ -198,11 +200,7 @@ 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
-        # 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
         assert np.all(a == b)
         assert not b.flags.owndata
         assert b.base is base

tests/test_numpy_dtypes.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import re
 
 import pytest

tests/test_numpy_vectorize.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import numpy_vectorize as m

tests/test_opaque_types.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import ConstructorStats, UserType

tests/test_operator_overloading.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import ConstructorStats

tests/test_pickling.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pickle
 import re
 

tests/test_python_multiple_inheritance.py

@@ -1,5 +1,6 @@
 # Adapted from:
 # https://github.com/google/clif/blob/5718e4d0807fd3b6a8187dde140069120b81ecef/clif/testing/python/python_multiple_inheritance_test.py
+from __future__ import annotations
 
 from pybind11_tests import python_multiple_inheritance as m
 

tests/test_pytypes.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import contextlib
 import sys
 import types

tests/test_sequences_and_iterators.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 from pytest import approx  # noqa: PT013
 

tests/test_smart_ptr.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 m = pytest.importorskip("pybind11_tests.smart_ptr")

tests/test_stl.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import ConstructorStats, UserType

tests/test_stl_binders.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import stl_binders as m

tests/test_tagbased_polymorphic.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pybind11_tests import tagbased_polymorphic as m
 
 

tests/test_thread.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import threading
 
 from pybind11_tests import thread as m

tests/test_type_caster_pyobject_ptr.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import type_caster_pyobject_ptr as m

tests/test_union.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pybind11_tests import union_ as m
 
 

tests/test_unnamed_namespace_a.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import unnamed_namespace_a as m

tests/test_unnamed_namespace_b.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pybind11_tests import unnamed_namespace_b as m
 
 

tests/test_vector_unique_ptr_member.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 from pybind11_tests import vector_unique_ptr_member as m

tests/test_virtual_functions.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import pytest
 
 import env  # noqa: F401

tools/FindPythonLibsNew.cmake

@@ -92,7 +92,7 @@ endif()
 
 # Use the Python interpreter to find the libs.
 if(NOT PythonLibsNew_FIND_VERSION)
-  set(PythonLibsNew_FIND_VERSION "3.6")
+  set(PythonLibsNew_FIND_VERSION "3.7")
 endif()
 
 if(NOT CMAKE_VERSION VERSION_LESS "3.27")

tools/codespell_ignore_lines_from_errors.py

@@ -9,11 +9,12 @@ python3 tools/codespell_ignore_lines_from_errors.py /tmp/codespell_errors.txt >
 git diff to review changes, then commit, push.
 """
 
+from __future__ import annotations
+
 import sys
-from typing import List
 
 
-def run(args: List[str]) -> None:
+def run(args: list[str]) -> None:
     assert len(args) == 1, "codespell_errors.txt"
     cache = {}
     done = set()

tools/libsize.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 import sys
 

tools/pybind11NewTools.cmake

@@ -56,7 +56,7 @@ if(NOT Python_FOUND AND NOT Python3_FOUND)
   endif()
 
   find_package(
-    Python 3.6 REQUIRED COMPONENTS ${_pybind11_interp_component} ${_pybind11_dev_component}
+    Python 3.7 REQUIRED COMPONENTS ${_pybind11_interp_component} ${_pybind11_dev_component}
                                    ${_pybind11_quiet} ${_pybind11_global_keyword})
 
   # If we are in submodule mode, export the Python targets to global targets.

tools/pybind11Tools.cmake

@@ -43,7 +43,7 @@ endif()
 
 # A user can set versions manually too
 set(Python_ADDITIONAL_VERSIONS
-    "3.12;3.11;3.10;3.9;3.8;3.7;3.6"
+    "3.12;3.11;3.10;3.9;3.8;3.7"
     CACHE INTERNAL "")
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}")