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Revision 9e3c42a15b03b3174d73b44e77befcf8864302ec authored by Fred Drake on 04 April 2002, 19:13:18 UTC, committed by Fred Drake on 04 April 2002, 19:13:18 UTC
We should get attributes from the right object.
1 parent eed9a44
Tip revision: 9e3c42a15b03b3174d73b44e77befcf8864302ec authored by Fred Drake on 04 April 2002, 19:13:18 UTC
Not sure why the regression test missed this, but the PyXML tests caught it.
Not sure why the regression test missed this, but the PyXML tests caught it.
Tip revision: 9e3c42a
shelve.py
"""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
__all__ = ["Shelf","BsdDbShelf","DbfilenameShelf","open"]
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 get(self, key, default=None):
if self.dict.has_key(key):
return self[key]
return default
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:
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)
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