Manage shelves of pickled objects.
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
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
Dependent on the implementation, closing a persistent dictionary may
or may not be necessary to flush changes to disk.
- Pickler(no arg info)
- Pickler(file, [binary]) -- Create a pickler
- If the optional argument, binary, is provided and is true, then
- pickles will be written in binary format, which is more space and
- computationally efficient.
- StringIO(no arg info)
- StringIO([s]) -- Return a StringIO-like stream for reading or writing
- Unpickler(no arg info)
- Unpickler(file) -- Create an unpickler
- open(filename, flag='c')
- Open a persistent dictionary for reading and writing.
- Argument is the filename for the dbm database.
- See the module's __doc__ string for an overview of the interface.