3.17 shelve -- Python object persistence

A ``shelf'' is a persistent, dictionary-like object. The difference with ``dbm'' databases is that the values (not the keys!) in a shelf can be essentially arbitrary Python objects -- anything that the pickle module can handle. This includes most class instances, recursive data types, and objects containing lots of shared sub-objects. The keys are ordinary strings.  

To summarize the interface (key is a string, data is an arbitrary object):

import shelve

d = shelve.open(filename) # open, with (g)dbm filename -- no suffix

d[key] = data   # store data at key (overwrites old data if
                # using an existing key)
data = d[key]   # retrieve data at key (raise KeyError if no
                # such key)
del d[key]      # delete data stored at key (raises KeyError
                # if no such key)
flag = d.has_key(key)   # true if the key exists
list = d.keys() # a list of all existing keys (slow!)

d.close()       # close it


See Also:

Module anydbm:
Generic interface to dbm-style databases.
Module dbhash:
BSD db database interface.
Module dbm:
Standard Unix database interface.
Module dumbdbm:
Portable implementation of the dbm interface.
Module gdbm:
GNU database interface, based on the dbm interface.
Module pickle:
Object serialization used by shelve.
Module cPickle:
High-performance version of pickle.
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