``` python
import os from os
import os
import pickle
class FileDescr(object):
saved = []
def __init__(self, name=None):
self.name = name
11
def __get__(self, obj, typ=None):
if self.name not in FileDescr.saved:
14 raise AttributeError, \
15 "%r used before assignment" % self.name
16
17 try:
18 f = open(self.name, 'r')
19 val = pickle.load(f)
20 f.close()
21 return val
22 except(pickle.InpicklingError, IOError,
23 EOFError, AttributeError,
24 ImportError, IndexError), e:
25 raise AttributeError, \
26 "could not read %r: %s" % self.name
27
28 def __set__(self, obj, val):
29 f = open(self.name, 'w')
30 try:
31 try:
32 pickle.dump(val, f)
33 FileDescr.saved.append(self.name)
34 except (TypeError, pickle.PicklingError), e:
35 raise AttributeError, \
36 "could not pickle %r" % self.name
37 finally:
38 f.close()
`這裏寫代碼片