mirror of
https://github.com/python/cpython.git
synced 2025-11-04 03:44:55 +00:00
153 lines
3.8 KiB
Python
153 lines
3.8 KiB
Python
"""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
|
|
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
|
|
|
|
Dependent on the implementation, closing a persistent dictionary may
|
|
or may not be necessary to flush changes to disk.
|
|
"""
|
|
|
|
# Try using cPickle and cStringIO if available.
|
|
|
|
try:
|
|
from cPickle import Pickler, Unpickler
|
|
except ImportError:
|
|
from pickle import Pickler, Unpickler
|
|
|
|
try:
|
|
from cStringIO import StringIO
|
|
except ImportError:
|
|
from StringIO import StringIO
|
|
|
|
|
|
class Shelf:
|
|
"""Base class for shelf implementations.
|
|
|
|
This is initialized with a dictionary-like object.
|
|
See the module's __doc__ string for an overview of the interface.
|
|
"""
|
|
|
|
def __init__(self, dict):
|
|
self.dict = dict
|
|
|
|
def keys(self):
|
|
return self.dict.keys()
|
|
|
|
def __len__(self):
|
|
return len(self.dict)
|
|
|
|
def has_key(self, key):
|
|
return self.dict.has_key(key)
|
|
|
|
def __getitem__(self, key):
|
|
f = StringIO(self.dict[key])
|
|
return Unpickler(f).load()
|
|
|
|
def __setitem__(self, key, value):
|
|
f = StringIO()
|
|
p = Pickler(f)
|
|
p.dump(value)
|
|
self.dict[key] = f.getvalue()
|
|
|
|
def __delitem__(self, key):
|
|
del self.dict[key]
|
|
|
|
def close(self):
|
|
try:
|
|
if self.dict:
|
|
self.dict.close()
|
|
except:
|
|
pass
|
|
self.dict = 0
|
|
|
|
def __del__(self):
|
|
self.close()
|
|
|
|
def sync(self):
|
|
if hasattr(self.dict, 'sync'):
|
|
self.dict.sync()
|
|
|
|
|
|
class BsdDbShelf(Shelf):
|
|
"""Shelf implementation using the "BSD" db interface.
|
|
|
|
This adds methods first(), next(), previous(), last() and
|
|
set_location() that have no counterpart in [g]dbm databases.
|
|
|
|
The actual database must be opened using one of the "bsddb"
|
|
modules "open" routines (i.e. bsddb.hashopen, bsddb.btopen or
|
|
bsddb.rnopen) and passed to the constructor.
|
|
|
|
See the module's __doc__ string for an overview of the interface.
|
|
"""
|
|
|
|
def __init__(self, dict):
|
|
Shelf.__init__(self, dict)
|
|
|
|
def set_location(self, key):
|
|
(key, value) = self.dict.set_location(key)
|
|
f = StringIO(value)
|
|
return (key, Unpickler(f).load())
|
|
|
|
def next(self):
|
|
(key, value) = self.dict.next()
|
|
f = StringIO(value)
|
|
return (key, Unpickler(f).load())
|
|
|
|
def previous(self):
|
|
(key, value) = self.dict.previous()
|
|
f = StringIO(value)
|
|
return (key, Unpickler(f).load())
|
|
|
|
def first(self):
|
|
(key, value) = self.dict.first()
|
|
f = StringIO(value)
|
|
return (key, Unpickler(f).load())
|
|
|
|
def last(self):
|
|
(key, value) = self.dict.last()
|
|
f = StringIO(value)
|
|
return (key, Unpickler(f).load())
|
|
|
|
|
|
class DbfilenameShelf(Shelf):
|
|
"""Shelf implementation using the "anydbm" generic dbm interface.
|
|
|
|
This is initialized with the filename for the dbm database.
|
|
See the module's __doc__ string for an overview of the interface.
|
|
"""
|
|
|
|
def __init__(self, filename, flag='c'):
|
|
import anydbm
|
|
Shelf.__init__(self, anydbm.open(filename, flag))
|
|
|
|
|
|
def 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.
|
|
"""
|
|
|
|
return DbfilenameShelf(filename, flag)
|