Index: Python/sysmodule.c
===================================================================
--- Python/sysmodule.c	(revision 41708)
+++ Python/sysmodule.c	(working copy)
@@ -1003,6 +1003,9 @@
 	PyDict_SetItemString(sysdict, "hexversion",
 			     v = PyInt_FromLong(PY_VERSION_HEX));
 	Py_XDECREF(v);
+	PyDict_SetItemString(sysdict, "build_number",
+			     v = PyInt_FromLong(Py_GetBuildNumber()));
+	Py_XDECREF(v);
 	/*
 	 * These release level checks are mutually exclusive and cover
 	 * the field, so don't get too fancy with the pre-processor!
Index: Include/pythonrun.h
===================================================================
--- Include/pythonrun.h	(revision 41708)
+++ Include/pythonrun.h	(working copy)
@@ -106,6 +106,7 @@
 PyAPI_FUNC(const char *) Py_GetCopyright(void);
 PyAPI_FUNC(const char *) Py_GetCompiler(void);
 PyAPI_FUNC(const char *) Py_GetBuildInfo(void);
+PyAPI_FUNC(int) Py_GetBuildNumber(void);
 
 /* Internal -- various one-time initializations */
 PyAPI_FUNC(PyObject *) _PyBuiltin_Init(void);
Index: Doc/lib/libsys.tex
===================================================================
--- Doc/lib/libsys.tex	(revision 41708)
+++ Doc/lib/libsys.tex	(working copy)
@@ -27,6 +27,11 @@
   \versionadded{2.0}
 \end{datadesc}
 
+\begin{datadesc}{build_number}
+  An integer representing the Subversion revision that this Python executable
+  was built from.
+\end{datadesc}  
+
 \begin{datadesc}{builtin_module_names}
   A tuple of strings giving the names of all modules that are compiled
   into this Python interpreter.  (This information is not available in
Index: Makefile.pre.in
===================================================================
--- Makefile.pre.in	(revision 41708)
+++ Makefile.pre.in	(working copy)
@@ -348,7 +348,9 @@
 		$(SIGNAL_OBJS) \
 		$(MODOBJS) \
 		$(srcdir)/Modules/getbuildinfo.c
-	if test -f buildno; then \
+	if test -d .svn; then \
+		svn info | grep -i revision | cut -f 2 -d " " >buildno; \
+	elif test -f buildno; then \
 		expr `cat buildno` + 1 >buildno1; \
 		mv -f buildno1 buildno; \
 	else echo 1 >buildno; fi
Index: Modules/getbuildinfo.c
===================================================================
--- Modules/getbuildinfo.c	(revision 41708)
+++ Modules/getbuildinfo.c	(working copy)
@@ -32,3 +32,9 @@
 		      "#%d, %.20s, %.9s", BUILD, DATE, TIME);
 	return buildinfo;
 }
+
+int
+Py_GetBuildNumber(void)
+{
+	return BUILD;
+}