Speed up loading and free memory...

[Josiah Carlson]

> files must not be modified, index file contains on one line a key and an
> offset which can be use to go directly to data file.

Keep the index in memory.

When you need to access a location that has an index in your data file:

data = open('data_file', 'rb')
data.seek(<index>)
data.read(<however much is needed>)

For most tasks, that should be fast enough.  If you want to cache some 
recently read data, check this cookbook entry:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/252524

  - Josiah