如何使用Python 2.7正确解开使用2.5腌制的内容？

Question

I am migrating a web app from Python 2.5 runtime to Python 2.7. My app stores pickled data into the database, and when unpickling what I stored I have some issues with long integers:

An int like 100003087328067, pickled using Python 2.5, gets unpickled to 2147483647 (which is 2^31-1) under Python 2.7.

How to retrieve the right value?

Can there be other issues? With str encoding for instance? (I found this but it's with python 3: Unpicking data pickled in Python 2.5, in Python 3.1 then uncompressing with zlib )

More about my context: I am migrating a Google App Engine app, and I stored my data using a custom db.Property that acts a bit like the NDB PickleProperty.

Answer 1

I would suggest a two stage setup:

Write a Python 2.5 script to unpickle the current values, store them with a common format like JSON, then read it back into a Python 2.7 app.

Ideally, continue to use a format like JSON rather than pickling, so that it isn't dependant on the platform in the future. Even better, store the data in the database as properly normalised data, so it can be used even more easily.