Today I had strange issue – I wrote some parsing code using BeautifulSoup 4.x which worked on localhost (in Windows environment), then uploaded to Appengine, and when parsing always got empty list instead of items. After hours of testing finally found that on GAE only BeautifulSoup 3.x works stable, doesn’t matters if you are using python 2.5 or 2.7.

So switched back to 3.2.1 and now got results again.