Because of my recent forays into Common Lisp and Haskell this recent recipe on ASPN piqued my interest. It demonstrates using Python source file encodings as a hook for introducing alternate Python syntax. Here's the simplest example of the technique I could come up with:

codec.py:

import codecs

class StreamReader(codecs.StreamReader):
   def decode(self, input, errors='strict'):
       output = input.replace('until ', 'while not ')
       output = output.replace('++', '+= 1')
       return unicode(output), len(input)

def get_my_codec(name):
   if name == 'play-language':
       return (codecs.utf_8_encode, None, StreamReader, None)

codecs.register(get_my_codec)

The above creates a codec called "play-language" and defines a very, very simple-minded source code transformation. For actual use, you'd need to work harder at parsing the code.

Now, if you create a file named play1.py with these contents:

# coding=play-language

c = 0
until c == 10:
   print c
   c++

And execute this from a command line:

python -c 'import codec1;import play1'

You'll get this output:

0
1
2
3
4
5
6
7
8
9