Update for all the various ways of checking for a string/unicode object

in 2.3, 2.2, 2.1/2.0.

pep-0008.txt

@@ -540,12 +540,23 @@ Programming Recommendations
         Yes: if isinstance(obj, int):
 
       When checking if an object is a string, keep in mind that it
-      might be a unicode string too!  In Python 2.2, the types module
-      has the StringTypes type defined for that purpose, e.g.:
+      might be a unicode string too!  In Python 2.3, str and unicode
+      have a common base class, basestring, so you can do:
 
-        from types import StringTypes:
+        if isinstance(strorunicodeobj, basestring):
+
+      In Python 2.2, the types module has the StringTypes type defined
+      for that purpose, e.g.:
+
+        from string import StringTypes
         if isinstance(strorunicodeobj, StringTypes):
 
+      In Python 2.0 and 2.1, you should do:
+
+        from string import StringType, UnicodeType
+        if isinstance(strorunicodeobj, StringType) or \
+           isinstance(strorunicodeobj, UnicodeType) :
+
     - For sequences, (strings, lists, tuples), use the fact that empty
       sequences are false, so "if not seq" or "if seq" is preferable
       to "if len(seq)" or "if not len(seq)".