--- /tmp/plistlib.py	2010-04-20 20:59:37.000000000 +0000
+++ plistlib.py	2011-02-02 18:56:26.000000000 +0000
@@ -81,15 +81,17 @@
     return rootObject
 
 
-def writePlist(rootObject, pathOrFile):
+def writePlist(rootObject, pathOrFile, ignoreNone=False):
     """Write 'rootObject' to a .plist file. 'pathOrFile' may either be a
-    file name or a (writable) file object.
+    file name or a (writable) file object. If 'ignoreNone' is set then
+    the writer will delete keys from the plist file that have a value of
+    None. Without this a TypeError is raised when None is encountered.
     """
     didOpen = 0
     if isinstance(pathOrFile, (str, unicode)):
         pathOrFile = open(pathOrFile, "w")
         didOpen = 1
-    writer = PlistWriter(pathOrFile)
+    writer = PlistWriter(pathOrFile, ignoreNone=ignoreNone)
     writer.writeln("<plist version=\"1.0\">")
     writer.writeValue(rootObject)
     writer.writeln("</plist>")
@@ -103,11 +105,12 @@
     return readPlist(StringIO(data))
 
 
-def writePlistToString(rootObject):
-    """Return 'rootObject' as a plist-formatted string.
+def writePlistToString(rootObject, ignoreNone=False):
+    """Return 'rootObject' as a plist-formatted string. `ignoreNone` is the
+    same as writePlist.
     """
     f = StringIO()
-    writePlist(rootObject, f)
+    writePlist(rootObject, f, ignoreNone)
     return f.getvalue()
 
 
@@ -229,9 +232,10 @@
 
 class PlistWriter(DumbXMLWriter):
 
-    def __init__(self, file, indentLevel=0, indent="\t", writeHeader=1):
+    def __init__(self, file, indentLevel=0, indent="\t", writeHeader=1, ignoreNone=False):
         if writeHeader:
             file.write(PLISTHEADER)
+        self.ignoreNone = ignoreNone
         DumbXMLWriter.__init__(self, file, indentLevel, indent)
 
     def writeValue(self, value):
@@ -277,6 +281,8 @@
         for key, value in items:
             if not isinstance(key, (str, unicode)):
                 raise TypeError("keys must be strings")
+            if self.ignoreNone and value is None:
+                continue
             self.simpleElement("key", key)
             self.writeValue(value)
         self.endElement("dict")
--- /mnt/home/bob/Python-2.7.1/Lib/test/test_plistlib.py	2010-04-21 06:00:35.000000000 +0000
+++ test_plistlib.py	2011-02-02 19:04:16.000000000 +0000
@@ -163,6 +163,33 @@
         pl2 = plistlib.readPlist(StringIO(f.getvalue()))
         self.assertEqual(dict(pl), dict(pl2))
 
+    def test_writing_none(self):
+        """Tests that the ignoreNone flag is working properly.
+
+        Generates plist files using writePlistToString() and writePlist().
+        Verifies that without ignoreNone a TypeError is raised and that
+        with ignoreNone generation succeeds. Also verifies that the two
+        methods are working the same.
+        """
+        from StringIO import StringIO
+        d = {
+            'key1': 'Something juicy',
+            'key2': None,
+        }
+        self.assertRaises(TypeError, plistlib.writePlistToString, d)
+        str_output = plistlib.writePlistToString(d, ignoreNone=True)
+
+        f = StringIO()
+        self.assertRaises(TypeError, plistlib.writePlist, d, f)
+
+        f = StringIO()
+        plistlib.writePlist(d, f, ignoreNone=True)
+        file_output = f.getvalue()
+
+        self.assertEqual(str_output, file_output)
+
+        plistlib.readPlistFromString(str_output)
+
     def test_controlcharacters(self):
         for i in range(128):
             c = chr(i)