Shelve: choice of database

Question

shelve documentation says:

The choice of which database package will be used (such as dbm, gdbm or bsddb) depends on which interface is available.

What is that mean? How to determine which package choosen? How to strictly define which one must be choosed? What database implementation best to use?

Answer 1

Found it here:
http://www.gossamer-threads.com/lists/python/python/13891

import shelve 
import gdbm 

def gdbm_shelve(filename, flag="c"): 
    return shelve.Shelf(gdbm.open(filename, flag)) 

db = gdbm_shelve("dbfile") 

ps
In linked page someone also found this somewhere, but his link is dead.