There is a wonderful writeup by PJ Eby about a Python codebase (Chandler) written by Java developers: http://dirtsimple.org/2004/12/python-is-not-java.html

Of note is that Java instincts are a bad thing for Python. Similar principles apply to other language combinations, and even services (eg SOAP vs REST) in addition to data as PJ wrote (eg XML vs JSON).