11.11. bsddb — Interface to Berkeley DB library

The bsddb module provides an interface to the Berkeley DB library. Users can create hash, btree or record based library files using the appropriate open call. Bsddb objects behave generally like dictionaries. Keys and values must be strings, however, so to use other objects as keys or to store other kinds of objects the user must serialize them somehow, typically using marshal.dumps() or pickle.dumps().

The bsddb module requires a Berkeley DB library version from 4.0 thru 4.7.

A more modern DB, DBEnv and DBSequence object interface is available in the bsddb.db module which closely matches the Berkeley DB C API documented at the above URLs. Additional features provided by the bsddb.db API include fine tuning, transactions, logging, and multiprocess concurrent database access.

The following is a description of the legacy bsddb interface compatible with the old Python bsddb module. Starting in Python 2.5 this interface should be safe for multithreaded access. The bsddb.db API is recommended for threading users as it provides better control.

The bsddb module defines the following functions that create objects that access the appropriate type of Berkeley DB file. The first two arguments of each function are the same. For ease of portability, only the first two arguments should be used in most instances.

bsddb.hashopen(filename[, flag[, mode[, pgsize[, ffactor[, nelem[, cachesize[, lorder[, hflags]]]]]]]])

Open the hash format file named filename. Files never intended to be preserved on disk may be created by passing None as the filename. The optional flag identifies the mode used to open the file. It may be 'r' (read only), 'w' (read-write), 'c' (read-write - create if necessary; the default) or 'n' (read-write - truncate to zero length). The other arguments are rarely used and are just passed to the low-level dbopen() function. Consult the Berkeley DB documentation for their use and interpretation.

bsddb.btopen(filename[, flag[, mode[, btflags[, cachesize[, maxkeypage[, minkeypage[, pgsize[, lorder]]]]]]]])

Open the btree format file named filename. Files never intended to be preserved on disk may be created by passing None as the filename. The optional flag identifies the mode used to open the file. It may be 'r' (read only), 'w' (read-write), 'c' (read-write - create if necessary; the default) or 'n' (read-write - truncate to zero length). The other arguments are rarely used and are just passed to the low-level dbopen function. Consult the Berkeley DB documentation for their use and interpretation.

bsddb.rnopen(filename[, flag[, mode[, rnflags[, cachesize[, pgsize[, lorder[, rlen[, delim[, source[, pad]]]]]]]]]])

Open a DB record format file named filename. Files never intended to be preserved on disk may be created by passing None as the filename. The optional flag identifies the mode used to open the file. It may be 'r' (read only), 'w' (read-write), 'c' (read-write - create if necessary; the default) or 'n' (read-write - truncate to zero length). The other arguments are rarely used and are just passed to the low-level dbopen function. Consult the Berkeley DB documentation for their use and interpretation.

>>> import bsddb
>>> db = bsddb.btopen('spam.db', 'c')
>>> for i in range(10): db['%d'%i] = '%d'% (i*i)
...
>>> db['3']
'9'
>>> db.keys()
['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
>>> db.first()
('0', '0')
>>> db.next()
('1', '1')
>>> db.last()
('9', '81')
>>> db.set_location('2')
('2', '4')
>>> db.previous()
('1', '1')
>>> for k, v in db.iteritems():
...     print k, v
0 0
1 1
2 4
3 9
4 16
5 25
6 36
7 49
8 64
9 81
>>> '8' in db
True
>>> db.sync()
0