1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
|
"""Weak reference support for Python.
This module is an implementation of PEP 205:
http://python.sourceforge.net/peps/pep-0205.html
"""
import UserDict
from _weakref import \
getweakrefcount, \
getweakrefs, \
ref, \
proxy, \
ReferenceError, \
CallableProxyType, \
ProxyType, \
ReferenceType
ProxyTypes = (ProxyType, CallableProxyType)
def mapping(dict=None):
return WeakDictionary(dict)
class WeakDictionary(UserDict.UserDict):
# We inherit the constructor without worrying about the input
# dictionary; since it uses our .update() method, we get the right
# checks (if the other dictionary is a WeakDictionary, objects are
# unwrapped on the way out, and we always wrap on the way in).
def __getitem__(self, key):
o = self.data.get(key)()
if o is None:
raise KeyError, key
else:
return o
def __repr__(self):
return "<WeakDictionary at %s>" % id(self)
def __setitem__(self, key, value):
def remove(o, data=self.data, key=key):
del data[key]
self.data[key] = ref(value, remove)
def copy(self):
new = WeakDictionary()
for key, ref in self.data.items():
o = ref()
if o is not None:
new[key] = o
def get(self, key, default):
try:
ref = self.data[key]
except KeyError:
return default
else:
o = ref()
if o is None:
# This should only happen
return default
else:
return o
def items(self):
L = []
for key, ref in self.data.items():
o = ref()
if o is not None:
L.append((key, o))
return L
def popitem(self):
while 1:
key, ref = self.data.popitem()
o = ref()
if o is not None:
return key, o
def setdefault(self, key, default):
try:
ref = self.data[key]
except KeyError:
def remove(o, data=self.data, key=key):
del data[key]
ref = ref(default, remove)
self.data[key] = ref
return default
else:
return ref()
def update(self, dict):
d = self.data
L = []
for key, o in dict.items():
def remove(o, data=d, key=key):
del data[key]
L.append(key, ref(o, remove))
for key, r in L:
d[key] = r
def values(self):
L = []
for ref in self.data.values():
o = ref()
if o is not None:
L.append(o)
return L
# no longer needed
del UserDict
|
