And here's a non-infinite example where CPython and PyPy differ.

Python 2.7.3 |EPD 7.3-1 (32-bit)| (default, Apr 12 2012, 11:28:34) 
[GCC 4.0.1 (Apple Inc. build 5493)] on darwin
Type "credits", "demo" or "enthought" for more information.
>>> b = [1]
>>> b += (x+1 for x in b if x < 5)
>>> b
[1, 2, 3, 4, 5]
>>> 
iwasawa:cpython mdickinson$ pypy-c
-bash: pypy-c: command not found
iwasawa:cpython mdickinson$ /opt/local/bin/pypy-c
Python 2.7.2 (341e1e3821fff77db3bb5cdb7a4851626298c44e, Jun 09 2012, 14:24:15)
[PyPy 1.9.0] on darwin
Type "help", "copyright", "credits" or "license" for more information.
And now for something completely different: ``'that's definitely a case of
"uh????"'''
>>>> b = [1]
>>>> b += (x+1 for x in b if x < 5)
>>>> b
[1, 2]