This section lists previously described changes that may require
changes to your code:
- Left shifts and hexadecimal/octal constants that are too 
  large no longer trigger a FutureWarning and return 
  a value limited to 32 or 64 bits; instead they return a long integer.
 
- Integer operations will no longer trigger an OverflowWarning.
The OverflowWarning warning will disappear in Python 2.5.
 
- The zip() built-in function and itertools.izip()
  now return  an empty list instead of raising a TypeError
  exception if called with no arguments.
 
- dircache.listdir() now passes exceptions to the caller
      instead of returning empty lists.
 
- LexicalHandler.startDTD() used to receive the public and
  system IDs in the wrong order.  This has been corrected; applications
  relying on the wrong order need to be fixed.
 
- fcntl.ioctl now warns if the mutate 
 argument is omitted and relevant.
 
- The tarfile module now generates GNU-format tar files
by default.
 
- Encountering a failure while importing a module no longer leaves
a partially-initialized module object in sys.modules.
 
- None is now a constant; code that binds a new value to 
the name "None" is now a syntax error.
 
See About this document... for information on suggesting changes.