#7301: add the environment variable $PYTHONWARNINGS to supplement the -W

command line option
patch from Brian Curtin

Doc/using/cmdline.rst

@@ -352,6 +352,8 @@ Miscellaneous options
 
       :pep:`230` -- Warning framework
 
+      :envvar:`PYTHONWARNINGS`
+
 
 .. cmdoption:: -x
 
@@ -547,6 +549,12 @@ These environment variables influence Python's behavior.
    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
 ~~~~~~~~~~~~~~~~~~~~

Lib/test/test_warnings.py

@@ -4,6 +4,7 @@ import os
 import StringIO
 import sys
 import unittest
+import subprocess
 from test import test_support
 
 import warning_tests
@@ -674,6 +675,42 @@ class PyCatchWarningTests(CatchWarningTests):
     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(), "['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(),
+                "['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(),
+                "['ignore::UnicodeWarning', 'ignore::DeprecationWarning']")
+
+class CEnvironmentVariableTests(EnvironmentVariableTests):
+    module = c_warnings
+
+class PyEnvironmentVariableTests(EnvironmentVariableTests):
+    module = py_warnings
+
+
 def test_main():
     py_warnings.onceregistry.clear()
     c_warnings.onceregistry.clear()
@@ -683,6 +720,8 @@ def test_main():
                                 _WarningsTests,
                                 CWarningsDisplayTests, PyWarningsDisplayTests,
                                 CCatchWarningTests, PyCatchWarningTests,
+                                CEnvironmentVariableTests,
+                                PyEnvironmentVariableTests
                              )
 
 

Misc/NEWS

@@ -12,6 +12,8 @@ What's New in Python 2.7 beta 1?
 Core and Builtins
 -----------------
 
+- Issue #7301: Add environment variable $PYTHONWARNINGS.
+
 - Issue #8329: Don't return the same lists from select.select when no fds are
   changed.
 

Modules/main.c

@@ -83,6 +83,7 @@ static char *usage_3 = "\
          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 = "\
@@ -420,6 +421,16 @@ Py_Main(int argc, char **argv)
 	    (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0')
 		Py_NoUserSiteDirectory = 1;
 
+	if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0')
+	{
+		char* warning = strtok(p, ",");
+		while (warning != NULL)
+		{
+			PySys_AddWarnOption(warning);
+			warning = strtok(NULL, ",");
+		}
+	}
+
 	if (command == NULL && module == NULL && _PyOS_optind < argc &&
 	    strcmp(argv[_PyOS_optind], "-") != 0)
 	{