YJL

While I was developing Last Tweets, I encountered a problem on production server, which is never happened on development server. The traceback looks like:

Traceback (most recent call last):
  File "/base/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line 499, in __call__
    handler.get(*groups)
  File "/base/data/home/apps/lastweet/1.12/index.py", line 77, in get
    'tweets': u._tweets_,
  File "/base/data/home/apps/lastweet/1.12/lastweet/user.py", line 47, in _get_tweets
    return pickle.loads(self.tweets)
  File "/base/python_dist/lib/python2.5/pickle.py", line 1367, in loads
    return Unpickler(file).load()
  File "/base/python_dist/lib/python2.5/pickle.py", line 852, in load
    dispatch[key](self)
KeyError: '\x00'
Traceback (most recent call last):
  File "/base/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line 499, in __call__
    handler.get(*groups)
  File "/base/data/home/apps/lastweet/1.12/index.py", line 77, in get
    'tweets': u._tweets_,
  File "/base/data/home/apps/lastweet/1.12/lastweet/user.py", line 47, in _get_tweets
    return pickle.loads(self.tweets)
  File "/base/python_dist/lib/python2.5/pickle.py", line 1367, in loads
    return Unpickler(file).load()
  File "/base/python_dist/lib/python2.5/pickle.py", line 852, in load
    dispatch[key](self)
KeyError: '\x00'

Where u._tweets_ is a property of data model class, defined as

_tweets_ = property(_get_tweets, _set_tweets)

A side note: when you need your own property (method or attribute), you need to prefix with an underscore _. Or GAE treats it as part of data. Even you have prefixed an underscore, if the name (_tweets) is same as a data field (tweets) and with property functions (_get_tweets), that may cause endless calls.

This error happens on when I use _get_tweets on production server, it does things like:

import pickle
...
return pickle.loads(self.tweets)

Then I got a KeyError. I resolved this with:

return pickle.loads(str(self.tweets))

It’s dirty. I still don’t know what Google did to pickle module. I got the pickled data and tried to unpickle on my computer, the result is correct. So that may only be something in unpickling. By the way, the tweets is a TextProperty.