gh-81773: Avoid parsing sys.version string in sysconfig

Lib/sysconfig/__init__.py

@@ -1,5 +1,6 @@
 """Access to Python's configuration information."""
 
+import _sysconfig
 import os
 import sys
 import threading
@@ -172,7 +173,7 @@ def joinuser(*args):
 _SCHEME_KEYS = ('stdlib', 'platstdlib', 'purelib', 'platlib', 'include',
                 'scripts', 'data')
 
-_PY_VERSION = sys.version.split()[0]
+_PY_VERSION = _sysconfig.PY_VERSION
 _PY_VERSION_SHORT = f'{sys.version_info[0]}.{sys.version_info[1]}'
 _PY_VERSION_SHORT_NO_DOT = f'{sys.version_info[0]}{sys.version_info[1]}'
 _BASE_PREFIX = os.path.normpath(sys.base_prefix)
@@ -385,7 +386,6 @@ def _init_non_posix(vars):
     """Initialize the module as appropriate for NT"""
     # set basic install directories
     import _winapi
-    import _sysconfig
     vars['LIBDEST'] = get_path('stdlib')
     vars['BINLIBDEST'] = get_path('platstdlib')
     vars['INCLUDEPY'] = get_path('include')
@@ -665,7 +665,6 @@ def get_platform():
 
     For other non-POSIX platforms, currently just returns :data:`sys.platform`."""
     if os.name == 'nt':
-        import _sysconfig
         platform = _sysconfig.get_platform()
         if platform:
             return platform

Lib/test/test_sysconfig.py

@@ -741,6 +741,14 @@ def test_sysconfig_config_vars_no_prefix_cache(self):
         self.assertEqual(config_vars['exec_prefix'], sys.exec_prefix)
         self.assertEqual(config_vars['platbase'], sys.exec_prefix)
 
+    def test_py_version(self):
+        config_vars = sysconfig.get_config_vars()
+        py_version = config_vars['py_version']
+        self.assertIsInstance(py_version, str)
+        ver = sys.version_info
+        version = f'{ver.major}.{ver.minor}.{ver.micro}'
+        self.assertStartsWith(py_version, version)
+
 
 class MakefileTests(unittest.TestCase):
 

Modules/_sysconfig.c

@@ -117,6 +117,14 @@ _sysconfig_get_platform_impl(PyObject *module)
 #endif  // MS_WINDOWS
 
 
+static int
+sysconfig_module_exec(PyObject *module)
+{
+    return PyModule_Add(module, "PY_VERSION",
+                        PyUnicode_FromString(PY_VERSION));
+}
+
+
 PyDoc_STRVAR(sysconfig__doc__,
 "A helper for the sysconfig module.");
 
@@ -127,6 +135,7 @@ static struct PyMethodDef sysconfig_methods[] = {
 };
 
 static PyModuleDef_Slot sysconfig_slots[] = {
+    {Py_mod_exec, sysconfig_module_exec},
     {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
     {Py_mod_gil, Py_MOD_GIL_NOT_USED},
     {0, NULL}