Merged revisions 59933-59951 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r59935 | raymond.hettinger | 2008-01-13 07:15:15 +0100 (Sun, 13 Jan 2008) | 1 line

  Named tuple is a concept, not a specific type.
........
  r59936 | raymond.hettinger | 2008-01-13 07:18:07 +0100 (Sun, 13 Jan 2008) | 1 line

  Fix spelling.
........
  r59937 | georg.brandl | 2008-01-13 10:36:18 +0100 (Sun, 13 Jan 2008) | 2 lines

  Clarify the effect of text mode.
........
  r59938 | thomas.heller | 2008-01-13 12:19:43 +0100 (Sun, 13 Jan 2008) | 1 line

  Make Modules/socketobject.c compile for Windows again.
........
  r59939 | ka-ping.yee | 2008-01-13 12:25:13 +0100 (Sun, 13 Jan 2008) | 9 lines

  Check in the patch proposed by Ben Hayden (benjhayden) for issue
  #1550: help('modules') broken by several 3rd party libraries.

  Tested with Python build: trunk:54235:59936M -- the reported error
  occurs with Django installed (or with any __init__.py present on
  the path that raises an exception), and such errors indeed go away
  when this change is applied.
........
  r59940 | georg.brandl | 2008-01-13 16:04:05 +0100 (Sun, 13 Jan 2008) | 2 lines

  Back out r59931 - test_ctypes fails with it.
........
  r59943 | amaury.forgeotdarc | 2008-01-14 01:22:44 +0100 (Mon, 14 Jan 2008) | 6 lines

  As discussed in issue 1700288:
  ctypes takes some liberties when creating python types: it modifies the types'
  __dict__ directly, bypassing all the machinery of type objects which deal with
  special methods.  And this broke recent optimisations of method lookup.
  Now we try to modify the type with more "official" functions.
........
  r59944 | amaury.forgeotdarc | 2008-01-14 01:29:41 +0100 (Mon, 14 Jan 2008) | 5 lines

  Re-apply patch #1700288 (first applied in r59931, rolled back in r59940)
  now that ctypes uses a more supported method to create types:

  Method cache optimization, by Armin Rigo, ported to 2.6 by Kevin Jacobs.
........
  r59946 | amaury.forgeotdarc | 2008-01-14 02:07:27 +0100 (Mon, 14 Jan 2008) | 4 lines

  ?Why did my tests not notice this before?
  Slots inheritance is very different from OO inheritance.
  This code lead to infinite recursion on classes derived from StructType.
........
  r59947 | christian.heimes | 2008-01-14 04:33:52 +0100 (Mon, 14 Jan 2008) | 1 line

  Added new an better structseq representation. E.g. repr(time.gmtime(0)) now returns 'time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=3, tm_yday=1, tm_isdst=0)' instead of '(1970, 1, 1, 0, 0, 0, 3, 1, 0)'. The feature is part of #1816: sys.flags
........
  r59948 | christian.heimes | 2008-01-14 04:35:38 +0100 (Mon, 14 Jan 2008) | 1 line

  I missed the most important file
........
  r59949 | christian.heimes | 2008-01-14 04:42:48 +0100 (Mon, 14 Jan 2008) | 1 line

  Applied patch #1816: sys.flags patch
........
  r59950 | christian.heimes | 2008-01-14 05:13:37 +0100 (Mon, 14 Jan 2008) | 2 lines

  Now that I've learnt about structseq objects I felt like converting sys.float_info to a structseq. It's
  readonly and help(sys.float_info) explains the attributes nicely.
........
  r59951 | christian.heimes | 2008-01-14 07:06:19 +0100 (Mon, 14 Jan 2008) | 1 line

  Added more comments to the new structseq repr code and implemented several of Neal's suggestions.
........

Doc/c-api/concrete.rst

@@ -433,7 +433,7 @@ Floating Point Objects
 
 .. cfunction:: PyObject* PyFloat_GetInfo(void)
 
-   Return a :ctype:`PyDictObject` object which contains information about the
+   Return a structseq instance which contains information about the
    precision, minimum and maximum values of a float. It's a thin wrapper
    around the header file :file:`float.h`.
 

Doc/glossary.rst

@@ -329,11 +329,17 @@ Glossary
       also :term:`immutable`.
 
    named tuple
-      A tuple subclass whose elements also are accessible as attributes via
+      Any tuple-like class whose indexable fields are also accessible with
-      fixed names (the class name and field names are indicated in the
+      named attributes (for example, :func:`time.localtime` returns a
-      individual documentation of a named tuple type, like ``TestResults(failed,
+      tuple-like object where the *year* is accessible either with an
-      attempted)``).  Named tuple classes are created by
+      index such as ``t[0]`` or with a named attribute like ``t.tm_year``).
-      :func:`collections.namedtuple`.
+
+      A named tuple can be a built-in type such as :class:`time.struct_time`,
+      or it can be created with a regular class definition.  A full featured
+      named tuple can also be created with the factory function
+      :func:`collections.namedtuple`.  The latter approach automatically
+      provides extra features such as a self-documenting representation like
+      ``Employee(name='jones', title='programmer')``.
     
    namespace
       The place where a variable is stored.  Namespaces are implemented as

Doc/library/functions.rst

@@ -743,10 +743,17 @@ available.  They are listed here in alphabetical order.
    * 'U' universal newline mode (for backwards compatibility;
      unnecessary in new code)
 
-   Combine ``'b'`` with ``'r'``, ``'w'``, or ``'a'``, for binary
+   The most commonly-used values of *mode* are ``'r'`` for reading, ``'w'`` for
-   mode, e.g., ``'rb'`` to open a file for reading in binary mode.
+   writing (truncating the file if it already exists), and ``'a'`` for appending
-   Modes ``'r+'``, ``'w+'`` and ``'a+'`` open the file for updating (note
+   (which on *some* Unix systems means that *all* writes append to the end of the
-   that ``'w+'`` truncates the file).
+   file regardless of the current seek position).  If *mode* is omitted, it
+   defaults to ``'r'``.  The default is to use text mode, which may convert
+   ``'\n'`` characters to a platform-specific representation on writing and back
+   on reading.  Thus, when opening a binary file, you should append ``'b'`` to
+   the *mode* value to open the file in binary mode, which will improve
+   portability.  (Appending ``'b'`` is useful even on systems that don't treat
+   binary and text files differently, where it serves as documentation.)  See below
+   for more possible values of *mode*.
 
    Python distinguishes between files opened in binary and text modes, even
    when the underlying operating system doesn't.  Files opened in binary

Doc/library/sys.rst

@@ -184,14 +184,52 @@ always available.
    error occurs.
 
 
+.. data:: flags
+
+   The struct sequence *flags* exposes the status of command line flags. The
+   attributes are read only.
+
+   +------------------------------+------------------------------------------+
+   | attribute                    | flag                                     |
+   +==============================+==========================================+
+   | :const:`debug`               | -d                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`py3k_warning`        | -3                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`division_warning`    | -Q                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`division_new`        | -Qnew                                    |
+   +------------------------------+------------------------------------------+
+   | :const:`inspect`             | -i                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`interactive`         | -i                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`optimize`            | -O or -OO                                |
+   +------------------------------+------------------------------------------+
+   | :const:`dont_write_bytecode` | -B                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`no_site`             | -S                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`ingnore_environment` | -E                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`tabcheck`            | -t or -tt                                |
+   +------------------------------+------------------------------------------+
+   | :const:`verbose`             | -v                                       |
+   +------------------------------+------------------------------------------+
+   | :const:`unicode`             | -U                                       |
+   +------------------------------+------------------------------------------+
+
+   .. versionadded:: 2.6
+
+
 .. data:: float_info
 
-   A dict holding information about the float type. It contains low level
+   A structseq holding information about the float type. It contains low level
    information about the precision and internal representation. Please study
    your system's :file:`float.h` for more information.
 
    +---------------------+--------------------------------------------------+
-   | key                 |  explanation                                     |
+   | attribute           |  explanation                                     |
    +=====================+==================================================+
    | :const:`epsilon`    | Difference between 1 and the next representable  |
    |                     | floating point number                            |

Lib/pydoc.py

@@ -1834,7 +1834,9 @@ Please wait a moment while I gather a list of all available modules...
                     modname = modname[:-9] + ' (package)'
                 if modname.find('.') < 0:
                     modules[modname] = 1
-            ModuleScanner().run(callback)
+            def onerror(modname):
+                callback(None, modname, None)
+            ModuleScanner().run(callback, onerror=onerror)
             self.list(modules.keys())
             self.output.write('''
 Enter any module name to get more help.  Or, type "modules spam" to search
@@ -1870,7 +1872,7 @@ class Scanner:
 class ModuleScanner:
     """An interruptible scanner that searches module synopses."""
 
-    def run(self, callback, key=None, completer=None):
+    def run(self, callback, key=None, completer=None, onerror=None):
         if key: key = key.lower()
         self.quit = False
         seen = {}
@@ -1887,7 +1889,7 @@ class ModuleScanner:
                     if name.lower().find(key) >= 0:
                         callback(None, modname, desc)
 
-        for importer, modname, ispkg in pkgutil.walk_packages():
+        for importer, modname, ispkg in pkgutil.walk_packages(onerror=onerror):
             if self.quit:
                 break
             if key is None:

Lib/test/test_structseq.py

@@ -28,7 +28,11 @@ class StructSeqTest(unittest.TestCase):
 
     def test_repr(self):
         t = time.gmtime()
-        repr(t)
+        self.assert_(repr(t))
+        t = time.gmtime(0)
+        self.assertEqual(repr(t),
+            "time.struct_time(tm_year=1970, tm_mon=1, tm_mday=1, tm_hour=0, "
+            "tm_min=0, tm_sec=0, tm_wday=3, tm_yday=1, tm_isdst=0)")
 
     def test_concat(self):
         t1 = time.gmtime()

Lib/test/test_sys.py

@@ -279,8 +279,8 @@ class SysModuleTest(unittest.TestCase):
         self.assert_(isinstance(sys.copyright, str))
         self.assert_(isinstance(sys.exec_prefix, str))
         self.assert_(isinstance(sys.executable, str))
-        self.assert_(isinstance(sys.float_info, dict))
         self.assertEqual(len(sys.float_info), 11)
+        self.assertEqual(sys.float_info.radix, 2)
         self.assert_(isinstance(sys.hexversion, int))
         self.assert_(isinstance(sys.maxsize, int))
         self.assert_(isinstance(sys.maxunicode, int))
@@ -320,6 +320,17 @@ class SysModuleTest(unittest.TestCase):
         self.assertRaises(TypeError, sys.intern, S("abc"))
 
 
+    def test_sys_flags(self):
+        self.failUnless(sys.flags)
+        attrs = ("debug", "division_warning",
+                 "inspect", "interactive", "optimize", "dont_write_bytecode",
+                 "no_site", "ingnore_environment", "tabcheck", "verbose")
+        for attr in attrs:
+            self.assert_(hasattr(sys.flags, attr), attr)
+            self.assertEqual(type(getattr(sys.flags, attr)), int, attr)
+        self.assert_(repr(sys.flags))
+
+
 def test_main():
     test.test_support.run_unittest(SysModuleTest)
 

Modules/_ctypes/_ctypes.c

@@ -401,7 +401,7 @@ static int
 StructType_setattro(PyObject *self, PyObject *key, PyObject *value)
 {
 	/* XXX Should we disallow deleting _fields_? */
-	if (-1 == PyObject_GenericSetAttr(self, key, value))
+	if (-1 == PyType_Type.tp_setattro(self, key, value))
 		return -1;
 	
 	if (value && PyUnicode_Check(key) &&

Modules/_ctypes/stgdict.c

@@ -458,7 +458,7 @@ StructUnionType_update_stgdict(PyObject *type, PyObject *fields, int isStruct)
 			Py_DECREF(pair);
 			return -1;
 		}
-		if (-1 == PyDict_SetItem(realdict, name, prop)) {
+		if (-1 == PyObject_SetAttr(type, name, prop)) {
 			Py_DECREF(prop);
 			Py_DECREF(pair);
 			return -1;

Modules/socketmodule.c

@@ -4979,10 +4979,13 @@ init_socket(void)
 #endif
 
 #ifdef SIO_RCVALL
-	tmp = PyLong_FromUnsignedLong(SIO_RCVALL);
+	{
-	if (tmp == NULL)
+		PyObject *tmp;
-		return;
+		tmp = PyLong_FromUnsignedLong(SIO_RCVALL);
-	PyModule_AddObject(m, "SIO_RCVALL", tmp);
+		if (tmp == NULL)
+			return;
+		PyModule_AddObject(m, "SIO_RCVALL", tmp);
+	}
 	PyModule_AddIntConstant(m, "RCVALL_OFF", RCVALL_OFF);
 	PyModule_AddIntConstant(m, "RCVALL_ON", RCVALL_ON);
 	PyModule_AddIntConstant(m, "RCVALL_SOCKETLEVELONLY", RCVALL_SOCKETLEVELONLY);

Objects/floatobject.c

@@ -5,6 +5,7 @@
    for any kind of float exception without losing portability. */
 
 #include "Python.h"
+#include "structseq.h"
 
 #include "formatter_unicode.h"
 
@@ -61,40 +62,87 @@ PyFloat_GetMin(void)
 	return DBL_MIN;
 }
 
+static PyTypeObject FloatInfoType;
+
+PyDoc_STRVAR(floatinfo__doc__,
+"sys.floatinfo\n\
+\n\
+A structseq holding information about the float type. It contains low level\n\
+information about the precision and internal representation. Please study\n\
+your system's :file:`float.h` for more information.");
+
+static PyStructSequence_Field floatinfo_fields[] = {
+	{"max",		"DBL_MAX -- maximum representable finite float"},
+	{"max_exp",	"DBL_MAX_EXP -- maximum int e such that radix**(e-1) "
+			"is representable"},
+	{"max_10_exp",	"DBL_MAX_10_EXP -- maximum int e such that 10**e "
+			"is representable"},
+	{"min",		"DBL_MIN -- Minimum positive normalizer float"},
+	{"min_exp",	"DBL_MIN_EXP -- minimum int e such that radix**(e-1) "
+			"is a normalized float"},
+	{"min_10_exp",	"DBL_MIN_10_EXP -- minimum int e such that 10**e is "
+			"a normalized"},
+	{"dig",		"DBL_DIG -- digits"},
+	{"mant_dig",	"DBL_MANT_DIG -- mantissa digits"},
+	{"epsilon",	"DBL_EPSILON -- Difference between 1 and the next "
+			"representable float"},
+	{"radix",	"FLT_RADIX -- radix of exponent"},
+	{"rounds",	"FLT_ROUNDS -- addition rounds"},
+	{0}
+};
+
+static PyStructSequence_Desc floatinfo_desc = {
+	"sys.floatinfo",	/* name */
+	floatinfo__doc__,	/* doc */
+	floatinfo_fields,	/* fields */
+	11
+};
+
 PyObject *
 PyFloat_GetInfo(void)
 {
-	PyObject *d, *tmp;
+	static PyObject* floatinfo;
+	int pos = 0;
 
-#define SET_FLOAT_CONST(d, key, const) \
+	if (floatinfo != NULL) {
-	tmp = PyFloat_FromDouble(const); \
+		Py_INCREF(floatinfo);
-	if (tmp == NULL) return NULL; \
+		return floatinfo;
-	if (PyDict_SetItemString(d, key, tmp)) return NULL; \
+	}
-	Py_DECREF(tmp)
+	PyStructSequence_InitType(&FloatInfoType, &floatinfo_desc);
-#define SET_INT_CONST(d, key, const) \
-	tmp = PyLong_FromLong(const); \
-	if (tmp == NULL) return NULL; \
-	if (PyDict_SetItemString(d, key, tmp)) return NULL; \
-	Py_DECREF(tmp)
 	
-	d = PyDict_New();
+	floatinfo = PyStructSequence_New(&FloatInfoType);
+	if (floatinfo == NULL) {
+		return NULL;
+	}
 
-	SET_FLOAT_CONST(d, "max", DBL_MAX);
+#define SetIntFlag(flag) \
-	SET_INT_CONST(d, "max_exp", DBL_MAX_EXP);
+	PyStructSequence_SET_ITEM(floatinfo, pos++, PyLong_FromLong(flag))
-	SET_INT_CONST(d, "max_10_exp", DBL_MAX_10_EXP);
+#define SetDblFlag(flag) \
-	SET_FLOAT_CONST(d, "min", DBL_MIN);
+	PyStructSequence_SET_ITEM(floatinfo, pos++, PyFloat_FromDouble(flag))
-	SET_INT_CONST(d, "min_exp", DBL_MIN_EXP);
-	SET_INT_CONST(d, "min_10_exp", DBL_MIN_10_EXP);
-	SET_INT_CONST(d, "dig", DBL_DIG);
-	SET_INT_CONST(d, "mant_dig", DBL_MANT_DIG);
-	SET_FLOAT_CONST(d, "epsilon", DBL_EPSILON);
-	SET_INT_CONST(d, "radix", FLT_RADIX);
-	SET_INT_CONST(d, "rounds", FLT_ROUNDS);
 
-	return d;
+	SetDblFlag(DBL_MAX);
+	SetIntFlag(DBL_MAX_EXP);
+	SetIntFlag(DBL_MAX_10_EXP);
+	SetDblFlag(DBL_MIN);
+	SetIntFlag(DBL_MIN_EXP);
+	SetIntFlag(DBL_MIN_10_EXP);
+	SetIntFlag(DBL_DIG);
+	SetIntFlag(DBL_MANT_DIG);
+	SetDblFlag(DBL_EPSILON);
+	SetIntFlag(FLT_RADIX);
+	SetIntFlag(FLT_ROUNDS);
+#undef SetIntFlag
+#undef SetDblFlag
+	
+	if (PyErr_Occurred()) {
+		Py_CLEAR(floatinfo);
+		return NULL;
+	}
+
+	Py_INCREF(floatinfo);
+	return floatinfo;
 }
 
-
 PyObject *
 PyFloat_FromDouble(double fval)
 {

Objects/structseq.c

@@ -230,11 +230,83 @@ make_tuple(PyStructSequence *obj)
 static PyObject *
 structseq_repr(PyStructSequence *obj)
 {
-	PyObject *tup, *str;
+	/* buffer and type size were chosen well considered. */
-	tup = make_tuple(obj);
+#define REPR_BUFFER_SIZE 512
-	str = PyObject_Repr(tup);
+#define TYPE_MAXSIZE 100
+
+	PyObject *tup;
+	PyTypeObject *typ = Py_TYPE(obj);
+	int i, removelast = 0;
+	Py_ssize_t len;
+	char buf[REPR_BUFFER_SIZE];
+	char *endofbuf, *pbuf = buf;
+
+	/* pointer to end of writeable buffer; safes space for "...)\0" */
+	endofbuf= &buf[REPR_BUFFER_SIZE-5];
+
+	if ((tup = make_tuple(obj)) == NULL) {
+		return NULL;
+	}
+
+	/* "typename(", limited to  TYPE_MAXSIZE */
+	len = strlen(typ->tp_name) > TYPE_MAXSIZE ? TYPE_MAXSIZE :
+						    strlen(typ->tp_name);
+	strncpy(pbuf, typ->tp_name, len);
+	pbuf += len;
+	*pbuf++ = '(';
+
+	for (i=0; i < VISIBLE_SIZE(obj); i++) {
+		PyObject *val, *repr;
+		char *cname, *crepr;
+
+		cname = typ->tp_members[i].name;
+		
+		val = PyTuple_GetItem(tup, i);
+		if (cname == NULL || val == NULL) {
+			return NULL;
+		}
+		repr = PyObject_Repr(val);
+		if (repr == NULL) {
+			Py_DECREF(tup);
+			return NULL;
+		}
+		crepr = PyUnicode_AsString(repr);
+		if (crepr == NULL) {
+			Py_DECREF(tup);
+			Py_DECREF(repr);
+			return NULL;
+		}
+		
+		/* + 3: keep space for "=" and ", " */
+ 		len = strlen(cname) + strlen(crepr) + 3;
+		if ((pbuf+len) <= endofbuf) {
+			strcpy(pbuf, cname);
+			pbuf += strlen(cname);
+			*pbuf++ = '=';
+			strcpy(pbuf, crepr);
+			pbuf += strlen(crepr);
+			*pbuf++ = ',';
+			*pbuf++ = ' ';
+			removelast = 1;
+			Py_DECREF(repr);
+		}
+		else {
+			strcpy(pbuf, "...");
+			pbuf += 3;
+			removelast = 0;
+			Py_DECREF(repr);
+			break;
+		}
+	}
 	Py_DECREF(tup);
-	return str;
+	if (removelast) {
+		/* overwrite last ", " */
+		pbuf-=2;
+	}
+	*pbuf++ = ')';
+	*pbuf = '\0';
+
+	return PyUnicode_FromString(buf);
 }
 
 static PyObject *

Python/sysmodule.c

@@ -15,6 +15,7 @@ Data members:
 */
 
 #include "Python.h"
+#include "structseq.h"
 #include "code.h"
 #include "frameobject.h"
 #include "eval.h"
@@ -1002,6 +1003,84 @@ Py_SubversionShortBranch()
 	return shortbranch;
 }
 
+
+PyDoc_STRVAR(flags__doc__,
+"sys.flags\n\
+\n\
+Flags provided through command line arguments or environment vars.");
+
+static PyTypeObject FlagsType;
+
+static PyStructSequence_Field flags_fields[] = {
+	{"debug",		"-d"},
+	{"division_warning",	"-Q"},
+	{"inspect",		"-i"},
+	{"interactive",		"-i"},
+	{"optimize",		"-O or -OO"},
+	{"dont_write_bytecode",	"-B"},
+	/* {"no_user_site",	"-s"}, */
+	{"no_site",		"-S"},
+	{"ingnore_environment",	"-E"},
+	{"tabcheck",		"-t or -tt"},
+	{"verbose",		"-v"},
+#ifdef RISCOS
+	{"ricos_wimp",		"???"},
+#endif
+	/* {"unbuffered",		"-u"}, */
+	/* {"skip_first",		"-x"}, */
+	{0}
+};
+
+static PyStructSequence_Desc flags_desc = {
+	"sys.flags",	/* name */
+	flags__doc__,	/* doc */
+	flags_fields,	/* fields */
+#ifdef RISCOS
+	11
+#else
+	10
+#endif
+};
+
+static PyObject*
+make_flags(void)
+{
+	int pos = 0;
+	PyObject *seq;
+
+	seq = PyStructSequence_New(&FlagsType);
+	if (seq == NULL)
+		return NULL;
+
+#define SetFlag(flag) \
+	PyStructSequence_SET_ITEM(seq, pos++, PyLong_FromLong(flag))
+
+	SetFlag(Py_DebugFlag);
+	SetFlag(Py_DivisionWarningFlag);
+	SetFlag(Py_InspectFlag);
+	SetFlag(Py_InteractiveFlag);
+	SetFlag(Py_OptimizeFlag);
+	SetFlag(Py_DontWriteBytecodeFlag);
+	/* SetFlag(Py_NoUserSiteDirectory); */
+	SetFlag(Py_NoSiteFlag);
+	SetFlag(Py_IgnoreEnvironmentFlag);
+	SetFlag(Py_TabcheckFlag);
+	SetFlag(Py_VerboseFlag);
+#ifdef RISCOS
+	SetFlag(Py_RISCOSWimpFlag);
+#endif
+	/* SetFlag(saw_unbuffered_flag); */
+	/* SetFlag(skipfirstline); */
+#undef SetFlag
+
+	if (PyErr_Occurred()) {
+		return NULL;
+	}
+
+	Py_INCREF(seq);
+	return seq;
+}
+
 PyObject *
 _PySys_Init(void)
 {
@@ -1041,9 +1120,9 @@ _PySys_Init(void)
 	v = Py_BuildValue("(UUU)", "CPython", branch, svn_revision);
 	PyDict_SetItemString(sysdict, "subversion", v);
 	Py_XDECREF(v);
-        PyDict_SetItemString(sysdict, "dont_write_bytecode",
+	PyDict_SetItemString(sysdict, "dont_write_bytecode",
-                             v = PyBool_FromLong(Py_DontWriteBytecodeFlag));
+			     v = PyBool_FromLong(Py_DontWriteBytecodeFlag));
-        Py_XDECREF(v);
+	Py_XDECREF(v);
 	/*
 	 * These release level checks are mutually exclusive and cover
 	 * the field, so don't get too fancy with the pre-processor!
@@ -1121,6 +1200,12 @@ _PySys_Init(void)
 		PyDict_SetItemString(sysdict, "warnoptions", warnoptions);
 	}
 
+	PyStructSequence_InitType(&FlagsType, &flags_desc);
+	PyDict_SetItemString(sysdict, "flags", make_flags());
+	/* prevent user from creating new instances */
+	FlagsType.tp_init = NULL;
+	FlagsType.tp_new = NULL;
+
 	if (PyErr_Occurred())
 		return NULL;
 	return m;