Index: src/org/python/core/PyString.java
===================================================================
--- src/org/python/core/PyString.java	(revision 4811)
+++ src/org/python/core/PyString.java	(working copy)
@@ -2186,6 +2186,99 @@
         }
         return super.unsupportedopMessage(op, o2);
     }
+
+    public PyList rsplit(){
+    	return str_rsplit(null,-1);
+    }
+
+    public PyList rsplit(String sep) {
+        return str_rsplit(sep, -1);
+    }
+
+    public PyList rsplit(String sep, int maxsplit) {
+        return str_rsplit(sep, maxsplit);
+    }
+
+    @ExposedMethod(defaults = {"null", "-1"})
+    final PyList str_rsplit(String sep, int maxsplit) {
+        if (sep != null) {
+            if (sep.length() == 0) {
+                throw Py.ValueError("empty separator");
+            }
+            PyList list = rsplitfields(sep,maxsplit);
+            list.reverse();
+            return list;
+        }
+        PyList list = new PyList();
+        char[] chars = string.toCharArray();
+        
+        if (maxsplit < 0)
+            maxsplit = chars.length;
+
+        int splits = 0;
+        int i = chars.length - 1;
+        
+        while(i > -1 && Character.isWhitespace(chars[i]))
+            i--;
+        if (i == -1)
+            return list;
+        
+        while (splits < maxsplit){
+            while(i > -1 && Character.isWhitespace(chars[i]))
+                i--;
+            if (i == -1)
+                break;
+            
+            int next_ws_char = i;
+            while (next_ws_char > -1 && !Character.isWhitespace(chars[next_ws_char]))
+                next_ws_char--;
+            if (next_ws_char == -1)
+                break;
+            
+            splits++;
+            list.add(fromSubstring(next_ws_char+1,i+1));
+            i = next_ws_char;
+        }
+        while (i > -1 && Character.isWhitespace(chars[i]))
+            i--;
+        if (i > -1)
+            list.add(fromSubstring(0,i+1));
+        //It'd be nice if lists supported a push() method.
+        // Can't use list.insert(0,foo) because a quadratic time would result.
+        list.reverse();
+        return list;
+    }
+    private PyList rsplitfields(String sep, int maxsplit) {
+        PyList list = new PyList();
+
+        int length = string.length();
+        if (maxsplit < 0)
+            maxsplit = length + 1;
+
+        int lastbreak = length;
+        int splits = 0;
+        int index = length;
+        int sepLength = sep.length();
+
+
+        while (index > 0  && splits < maxsplit){
+            int i = string.lastIndexOf(sep,index-sepLength);
+            if (i == index)
+            {
+        	i -= sepLength;
+            }
+            if (i < 0)
+        	break;
+            splits++;
+            list.append(fromSubstring(i+sepLength,lastbreak));
+            lastbreak = i;
+            index = i;
+            
+        }
+        list.append(fromSubstring(0,lastbreak));
+        //list.reverse();
+        return list;
+    }
 }
 
 final class StringFormatter
Index: Lib/test/string_tests.py
===================================================================
--- Lib/test/string_tests.py	(revision 4811)
+++ Lib/test/string_tests.py	(working copy)
@@ -185,10 +185,100 @@
         self.checkequal(['a', 'b', 'c  d'], 'a  b  c  d', 'split', None, 2)
         self.checkequal(['a', 'b', 'c', 'd'], 'a b c d ', 'split')
         self.checkequal(['a', 'b', 'c', 'd'], 'a//b//c//d', 'split', '//')
-        #self.checkequal(['endcase ', ''], 'endcase test', 'split', 'test')
 
         self.checkraises(TypeError, 'hello', 'split', 42, 42, 42)
+        self.checkraises(ValueError, 'hello', 'split', "",42)
+        self.checkraises(ValueError, 'hello', 'split', "")
+    def test_rsplit(self):
+        self.checkequal(['this', 'is', 'the', 'rsplit', 'function'],
+                         'this is the rsplit function', 'rsplit')
 
+        # by whitespace
+        self.checkequal(['a', 'b', 'c', 'd'], 'a b c d ', 'rsplit')
+        self.checkequal(['a b c', 'd'], 'a b c d', 'rsplit', None, 1)
+        self.checkequal(['a b', 'c', 'd'], 'a b c d', 'rsplit', None, 2)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a b c d', 'rsplit', None, 3)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a b c d', 'rsplit', None, 4)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a b c d', 'rsplit', None,
+                        sys.maxint-20)
+        self.checkequal(['a b c d'], 'a b c d', 'rsplit', None, 0)
+        self.checkequal(['a b c d'], 'a b c d  ', 'rsplit', None, 0)
+        self.checkequal(['a  b', 'c', 'd'], 'a  b  c  d', 'rsplit', None, 2)
+
+        self.checkequal([], '         ', 'rsplit')
+        self.checkequal(['a'], '  a    ', 'rsplit')
+        self.checkequal(['a', 'b'], '  a    b   ', 'rsplit')
+        self.checkequal(['  a', 'b'], '  a    b   ', 'rsplit', None, 1)
+        self.checkequal(['  a    b','c'], '  a    b   c   ', 'rsplit',
+                        None, 1)
+        self.checkequal(['  a', 'b', 'c'], '  a    b   c   ', 'rsplit',
+                        None, 2)
+        self.checkequal(['a', 'b'], '\n\ta \t\r b \v ', 'rsplit', None, 88)
+        aaa = ' a '*20
+        self.checkequal(['a']*20, aaa, 'rsplit')
+        self.checkequal([aaa[:-4]] + ['a'], aaa, 'rsplit', None, 1)
+        self.checkequal([' a  a'] + ['a']*18, aaa, 'rsplit', None, 18)
+
+
+        # by a char
+        self.checkequal(['a', 'b', 'c', 'd'], 'a|b|c|d', 'rsplit', '|')
+        self.checkequal(['a|b|c', 'd'], 'a|b|c|d', 'rsplit', '|', 1)
+        self.checkequal(['a|b', 'c', 'd'], 'a|b|c|d', 'rsplit', '|', 2)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a|b|c|d', 'rsplit', '|', 3)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a|b|c|d', 'rsplit', '|', 4)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a|b|c|d', 'rsplit', '|',
+                        sys.maxint-100)
+        self.checkequal(['a|b|c|d'], 'a|b|c|d', 'rsplit', '|', 0)
+        self.checkequal(['a||b||c', '', 'd'], 'a||b||c||d', 'rsplit', '|', 2)
+        self.checkequal(['', ' begincase'], '| begincase', 'rsplit', '|')
+        self.checkequal(['endcase ', ''], 'endcase |', 'rsplit', '|')
+        self.checkequal(['', 'bothcase', ''], '|bothcase|', 'rsplit', '|')
+
+        self.checkequal(['a\x00\x00b', 'c', 'd'], 'a\x00\x00b\x00c\x00d', 'rsplit', '\x00', 2)
+
+        #self.checkequal(['a']*20, ('a|'*20)[:-1], 'rsplit', '|')
+        self.checkequal(['a|a|a|a|a']+['a']*15,
+                        ('a|'*20)[:-1], 'rsplit', '|', 15)
+
+        # by string
+        self.checkequal(['a', 'b', 'c', 'd'], 'a//b//c//d', 'rsplit', '//')
+        self.checkequal(['a//b//c', 'd'], 'a//b//c//d', 'rsplit', '//', 1)
+        self.checkequal(['a//b', 'c', 'd'], 'a//b//c//d', 'rsplit', '//', 2)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a//b//c//d', 'rsplit', '//', 3)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a//b//c//d', 'rsplit', '//', 4)
+        self.checkequal(['a', 'b', 'c', 'd'], 'a//b//c//d', 'rsplit', '//',
+                        sys.maxint-5)
+        self.checkequal(['a//b//c//d'], 'a//b//c//d', 'rsplit', '//', 0)
+        self.checkequal(['a////b////c', '', 'd'], 'a////b////c////d', 'rsplit', '//', 2)
+        self.checkequal(['', ' begincase'], 'test begincase', 'rsplit', 'test')
+        self.checkequal(['endcase ', ''], 'endcase test', 'rsplit', 'test')
+        self.checkequal(['', ' bothcase ', ''], 'test bothcase test',
+                        'rsplit', 'test')
+        self.checkequal(['ab', 'c'], 'abbbc', 'rsplit', 'bb')
+        self.checkequal(['', ''], 'aaa', 'rsplit', 'aaa')
+        self.checkequal(['aaa'], 'aaa', 'rsplit', 'aaa', 0)
+        self.checkequal(['ab', 'ab'], 'abbaab', 'rsplit', 'ba')
+        self.checkequal(['aaaa'], 'aaaa', 'rsplit', 'aab')
+        self.checkequal([''], '', 'rsplit', 'aaa')
+        self.checkequal(['aa'], 'aa', 'rsplit', 'aaa')
+        self.checkequal(['bbob', 'A'], 'bbobbbobbA', 'rsplit', 'bbobb')
+        self.checkequal(['', 'B', 'A'], 'bbobbBbbobbA', 'rsplit', 'bbobb')
+
+        self.checkequal(['a']*20, ('aBLAH'*20)[:-4], 'rsplit', 'BLAH')
+        self.checkequal(['a']*20, ('aBLAH'*20)[:-4], 'rsplit', 'BLAH', 19)
+        self.checkequal(['aBLAHa'] + ['a']*18, ('aBLAH'*20)[:-4],
+                        'rsplit', 'BLAH', 18)
+
+        # mixed use of str and unicode
+        self.checkequal([u'a b', u'c', u'd'], 'a b c d', 'rsplit', u' ', 2)
+
+        # argument type
+        self.checkraises(TypeError, 'hello', 'rsplit', 42, 42, 42)
+
+        # null case
+        self.checkraises(ValueError, 'hello', 'rsplit', '')
+        self.checkraises(ValueError, 'hello', 'rsplit', '', 0)
+
     def test_strip(self):
         self.checkequal('hello', '   hello   ', 'strip')
         self.checkequal('hello   ', '   hello   ', 'lstrip')