Index: Include/Python.h
===================================================================
--- Include/Python.h	(revision 79880)
+++ Include/Python.h	(working copy)
@@ -123,6 +123,9 @@
 /* _Py_Mangle is defined in compile.c */
 PyAPI_FUNC(PyObject*) _Py_Mangle(PyObject *p, PyObject *name);
 
+/* _Py_char2wchar lives in python.c */
+PyAPI_FUNC(wchar_t *) _Py_char2wchar(char *);
+
 /* Convert a possibly signed character to a nonnegative int */
 /* XXX This assumes characters are 8 bits wide */
 #ifdef __CHAR_UNSIGNED__
Index: Misc/python.man
===================================================================
--- Misc/python.man	(revision 79880)
+++ Misc/python.man	(working copy)
@@ -394,6 +394,9 @@
 If this is set to a non-empty string it is equivalent to specifying
 the \fB\-v\fP option. If set to an integer, it is equivalent to
 specifying \fB\-v\fP multiple times. 
+.IP PYTHONWARNINGS
+If this is set to a comma-separated string it is equivalent to
+specifying the \fB\-W\fP option for each separate value.
 .SH AUTHOR
 The Python Software Foundation: http://www.python.org/psf
 .SH INTERNET RESOURCES
Index: Doc/using/cmdline.rst
===================================================================
--- Doc/using/cmdline.rst	(revision 79880)
+++ Doc/using/cmdline.rst	(working copy)
@@ -1,5 +1,8 @@
 .. highlightlang:: none
 
+.. ATTENTION: You probably should update Misc/python.man, too, if you modify
+.. this file.
+
 .. _using-on-general:
 
 Command line and environment
@@ -306,6 +309,8 @@
 
       :pep:`230` -- Warning framework
 
+      :envvar:`PYTHONWARNINGS`
+
 
 .. cmdoption:: -x
 
@@ -469,6 +474,12 @@
    value instead of the value got through the C runtime.  Only works on
    Mac OS X.
 
+.. envvar:: PYTHONWARNINGS
+
+   This is the equivalent to the :option:`-W` option. If set to a comma
+   separated string, it is equivalent to specifying :option:`-W` multiple
+   times.
+
 
 Debug-mode variables
 ~~~~~~~~~~~~~~~~~~~~
Index: Lib/test/test_warnings.py
===================================================================
--- Lib/test/test_warnings.py	(revision 79880)
+++ Lib/test/test_warnings.py	(working copy)
@@ -4,6 +4,7 @@
 from io import StringIO
 import sys
 import unittest
+import subprocess
 from test import support
 
 from test import warning_tests
@@ -685,6 +686,52 @@
     module = py_warnings
 
 
+class EnvironmentVariableTests(BaseTest):
+
+    def test_single_warning(self):
+        newenv = os.environ.copy()
+        newenv["PYTHONWARNINGS"] = "ignore::DeprecationWarning"
+        p = subprocess.Popen([sys.executable,
+                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
+                stdout=subprocess.PIPE, env=newenv)
+        self.assertEqual(p.stdout.read(), b"['ignore::DeprecationWarning']")
+
+    def test_comma_separated_warnings(self):
+        newenv = os.environ.copy()
+        newenv["PYTHONWARNINGS"] = ("ignore::DeprecationWarning,"
+                                    "ignore::UnicodeWarning")
+        p = subprocess.Popen([sys.executable,
+                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
+                stdout=subprocess.PIPE, env=newenv)
+        self.assertEqual(p.stdout.read(),
+                b"['ignore::DeprecationWarning', 'ignore::UnicodeWarning']")
+
+    def test_envvar_and_command_line(self):
+        newenv = os.environ.copy()
+        newenv["PYTHONWARNINGS"] = "ignore::DeprecationWarning"
+        p = subprocess.Popen([sys.executable, "-W" "ignore::UnicodeWarning",
+                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
+                stdout=subprocess.PIPE, env=newenv)
+        self.assertEqual(p.stdout.read(),
+                b"['ignore::UnicodeWarning', 'ignore::DeprecationWarning']")
+
+    def test_nonascii(self):
+        newenv = os.environ.copy()
+        newenv["PYTHONWARNINGS"] = "ignore:DeprecaciónWarning"
+        newenv["PYTHONIOENCODING"] = "utf-8"
+        p = subprocess.Popen([sys.executable,
+                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
+                stdout=subprocess.PIPE, env=newenv)
+        self.assertEqual(p.stdout.read(),
+                "['ignore:DeprecaciónWarning']".encode('utf-8'))
+
+class CEnvironmentVariableTests(EnvironmentVariableTests):
+    module = c_warnings
+
+class PyEnvironmentVariableTests(EnvironmentVariableTests):
+    module = py_warnings
+
+
 def test_main():
     py_warnings.onceregistry.clear()
     c_warnings.onceregistry.clear()
@@ -696,6 +743,8 @@
                                 _WarningsTests,
                                 CWarningsDisplayTests, PyWarningsDisplayTests,
                                 CCatchWarningTests, PyCatchWarningTests,
+                                CEnvironmentVariableTests,
+                                PyEnvironmentVariableTests
                              )
 
 
Index: Modules/python.c
===================================================================
--- Modules/python.c	(revision 79880)
+++ Modules/python.c	(working copy)
@@ -14,8 +14,8 @@
 	return Py_Main(argc, argv);
 }
 #else
-static wchar_t*
-char2wchar(char* arg)
+wchar_t*
+_Py_char2wchar(char* arg)
 {
 	wchar_t *res;
 #ifdef HAVE_BROKEN_MBSTOWCS
@@ -143,7 +143,7 @@
 	oldloc = strdup(setlocale(LC_ALL, NULL));
 	setlocale(LC_ALL, "");
 	for (i = 0; i < argc; i++) {
-		argv_copy2[i] = argv_copy[i] = char2wchar(argv[i]);
+		argv_copy2[i] = argv_copy[i] = _Py_char2wchar(argv[i]);
 		if (!argv_copy[i])
 			return 1;
 	}
Index: Modules/main.c
===================================================================
--- Modules/main.c	(revision 79880)
+++ Modules/main.c	(working copy)
@@ -82,6 +82,7 @@
          can be supplied multiple times to increase verbosity\n\
 -V     : print the Python version number and exit (also --version)\n\
 -W arg : warning control; arg is action:message:category:module:lineno\n\
+         also PYTHONWARNINGS=arg\n\
 -x     : skip first line of source, allowing use of non-Unix forms of #!cmd\n\
 ";
 static char *usage_4 = "\
@@ -265,6 +266,9 @@
 	wchar_t *module = NULL;
 	FILE *fp = stdin;
 	char *p;
+#ifdef MS_WINDOWS
+	wchar_t *wp;
+#endif
 	int skipfirstline = 0;
 	int stdin_is_interactive = 0;
 	int help = 0;
@@ -401,6 +405,47 @@
 	    (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0')
 		Py_NoUserSiteDirectory = 1;
 
+#ifdef MS_WINDOWS
+	if (!Py_IgnoreEnvironmentFlag && (wp = _wgetenv(L"PYTHONWARNINGS")) &&
+	    *wp != L'\0') {
+		wchar_t *buf, *warning;
+
+		buf = (wchar_t *)malloc((wcslen(wp) + 1) * sizeof(wchar_t));
+		if (buf == NULL)
+			Py_FatalError(
+			   "not enough memory to copy PYTHONWARNINGS");
+		wcscpy(buf, wp);
+		for (warning = wcstok(buf, L",");
+		     warning != NULL;
+		     warning = wcstok(NULL, L",")) {
+			PySys_AddWarnOption(warning);
+		}
+		free(buf);
+	}
+#else
+	if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0') {
+		char *buf, *oldloc;
+		wchar_t *warning;
+
+		buf = (char *)malloc(strlen(p) + 1);
+		if (buf == NULL)
+			Py_FatalError(
+			   "not enough memory to copy PYTHONWARNINGS");
+		strcpy(buf, p);
+		oldloc = strdup(setlocale(LC_ALL, NULL));
+		setlocale(LC_ALL, "");
+		for (p = strtok(buf, ","); p != NULL; p = strtok(NULL, ",")) {
+			if ((warning = _Py_char2wchar(p)) != NULL) {
+				PySys_AddWarnOption(warning);
+				free(warning);
+			}
+		}
+		setlocale(LC_ALL, oldloc);
+		free(oldloc);
+		free(buf);
+	}
+#endif
+
 	if (command == NULL && module == NULL && _PyOS_optind < argc &&
 	    wcscmp(argv[_PyOS_optind], L"-") != 0)
 	{