[3.13] gh-145990: sort --help-env first section by name (others and xoptions already sorted) (GH-146003)

* sort `--help-env` sections by environment variable name
  Only needed in the first section, in 3.13 the second section was already sorted.
* regression test for --help-env & --help-xoptions sort order

Manual backport of GH-145997

Author: gpshead

Lib/test/test_cmd_line.py

@@ -3,6 +3,7 @@
 # See test_cmd_line_script.py for testing of script execution
 
 import os
+import re
 import subprocess
 import sys
 import tempfile
@@ -54,11 +55,22 @@ def test_help(self):
     def test_help_env(self):
         out = self.verify_valid_flag('--help-env')
         self.assertIn(b'PYTHONHOME', out)
+        # Env vars in each section should be sorted alphabetically
+        # (ignoring underscores so PYTHON_FOO and PYTHONFOO intermix naturally)
+        sort_key = lambda name: name.replace(b'_', b'').lower()
+        sections = out.split(b'These variables have equivalent')
+        for section in sections:
+            envvars = re.findall(rb'^(PYTHON\w+)', section, re.MULTILINE)
+            self.assertEqual(envvars, sorted(envvars, key=sort_key),
+                             "env vars should be sorted alphabetically")
 
     @support.cpython_only
     def test_help_xoptions(self):
         out = self.verify_valid_flag('--help-xoptions')
         self.assertIn(b'-X dev', out)
+        options = re.findall(rb'^-X (\w+)', out, re.MULTILINE)
+        self.assertEqual(options, sorted(options),
+                         "options should be sorted alphabetically")
 
     @support.cpython_only
     def test_help_all(self):

Misc/NEWS.d/next/Core_and_Builtins/2026-03-15-21-45-35.gh-issue-145990.tmXwRB.rst

@@ -0,0 +1 @@
+``python --help-env`` sections are now sorted by environment variable name.

Python/initconfig.c

@@ -238,32 +238,32 @@ The following implementation-specific options are available:\n\
 /* Envvars that don't have equivalent command-line options are listed first */
 static const char usage_envvars[] =
 "Environment variables that change behavior:\n"
-"PYTHONSTARTUP   : file executed on interactive startup (no default)\n"
-"PYTHONPATH      : '%lc'-separated list of directories prefixed to the\n"
-"                  default module search path.  The result is sys.path.\n"
-"PYTHONHOME      : alternate <prefix> directory (or <prefix>%lc<exec_prefix>).\n"
-"                  The default module search path uses %s.\n"
-"PYTHONPLATLIBDIR: override sys.platlibdir\n"
+"PYTHONBREAKPOINT: if this variable is set to 0, it disables the default\n"
+"                  debugger.  It can be set to the callable of your debugger of\n"
+"                  choice.\n"
 "PYTHONCASEOK    : ignore case in 'import' statements (Windows)\n"
-"PYTHONIOENCODING: encoding[:errors] used for stdin/stdout/stderr\n"
-"PYTHONHASHSEED  : if this variable is set to 'random', a random value is used\n"
-"                  to seed the hashes of str and bytes objects.  It can also be\n"
-"                  set to an integer in the range [0,4294967295] to get hash\n"
-"                  values with a predictable seed.\n"
-"PYTHONMALLOC    : set the Python memory allocators and/or install debug hooks\n"
-"                  on Python memory allocators.  Use PYTHONMALLOC=debug to\n"
-"                  install debug hooks.\n"
 "PYTHONCOERCECLOCALE: if this variable is set to 0, it disables the locale\n"
 "                  coercion behavior.  Use PYTHONCOERCECLOCALE=warn to request\n"
 "                  display of locale coercion and locale compatibility warnings\n"
 "                  on stderr.\n"
-"PYTHONBREAKPOINT: if this variable is set to 0, it disables the default\n"
-"                  debugger.  It can be set to the callable of your debugger of\n"
-"                  choice.\n"
 "PYTHON_COLORS   : if this variable is set to 1, the interpreter will colorize\n"
 "                  various kinds of output.  Setting it to 0 deactivates\n"
 "                  this behavior.\n"
+"PYTHONHASHSEED  : if this variable is set to 'random', a random value is used\n"
+"                  to seed the hashes of str and bytes objects.  It can also be\n"
+"                  set to an integer in the range [0,4294967295] to get hash\n"
+"                  values with a predictable seed.\n"
 "PYTHON_HISTORY  : the location of a .python_history file.\n"
+"PYTHONHOME      : alternate <prefix> directory (or <prefix>%lc<exec_prefix>).\n"
+"                  The default module search path uses %s.\n"
+"PYTHONIOENCODING: encoding[:errors] used for stdin/stdout/stderr\n"
+"PYTHONMALLOC    : set the Python memory allocators and/or install debug hooks\n"
+"                  on Python memory allocators.  Use PYTHONMALLOC=debug to\n"
+"                  install debug hooks.\n"
+"PYTHONPATH      : '%lc'-separated list of directories prefixed to the\n"
+"                  default module search path.  The result is sys.path.\n"
+"PYTHONPLATLIBDIR: override sys.platlibdir\n"
+"PYTHONSTARTUP   : file executed on interactive startup (no default)\n"
 "\n"
 "These variables have equivalent command-line options (see --help for details):\n"
 "PYTHON_CPU_COUNT: override the return value of os.cpu_count() (-X cpu_count)\n"
@@ -2407,7 +2407,7 @@ config_usage(int error, const wchar_t* program)
 static void
 config_envvars_usage(void)
 {
-    printf(usage_envvars, (wint_t)DELIM, (wint_t)DELIM, PYTHONHOMEHELP);
+    printf(usage_envvars, (wint_t)DELIM, PYTHONHOMEHELP, (wint_t)DELIM);
 }
 
 static void