Lib/weakref.py

   1 """Weak reference support for Python.
   2
   3 This module is an implementation of PEP 205:
   4
   5 http://python.sourceforge.net/peps/pep-0205.html
   6 """
   7
   8 import UserDict
   9
  10 from _weakref import \
  11      getweakrefcount, \
  12      getweakrefs, \
  13      ref, \
  14      proxy, \
  15      ReferenceError, \
  16      CallableProxyType, \
  17      ProxyType, \
  18      ReferenceType
  19
  20 ProxyTypes = (ProxyType, CallableProxyType)
  21
  22 __all__ = ["ref", "mapping", "proxy", "getweakrefcount", "getweakrefs",
  23            "WeakKeyDictionary", "ReferenceType", "ProxyType",
  24            "CallableProxyType", "ProxyTypes", "WeakValueDictionary"]
  25
  26 def mapping(dict=None,weakkeys=0):
  27     if weakkeys:
  28         return WeakKeyDictionary(dict)
  29     else:
  30         return WeakValueDictionary(dict)
  31
  32
  33 class WeakValueDictionary(UserDict.UserDict):
  34
  35     # We inherit the constructor without worrying about the input
  36     # dictionary; since it uses our .update() method, we get the right
  37     # checks (if the other dictionary is a WeakValueDictionary,
  38     # objects are unwrapped on the way out, and we always wrap on the
  39     # way in).
  40
  41     def __getitem__(self, key):
  42         o = self.data.get(key)()
  43         if o is None:
  44             raise KeyError, key
  45         else:
  46             return o
  47
  48     def __repr__(self):
  49         return "<WeakValueDictionary at %s>" % id(self)
  50
  51     def __setitem__(self, key, value):
  52         def remove(o, data=self.data, key=key):
  53             del data[key]
  54         self.data[key] = ref(value, remove)
  55
  56     def copy(self):
  57         new = WeakValueDictionary()
  58         for key, ref in self.data.items():
  59             o = ref()
  60             if o is not None:
  61                 new[key] = o
  62         return new
  63
  64     def get(self, key, default):
  65         try:
  66             ref = self.data[key]
  67         except KeyError:
  68             return default
  69         else:
  70             o = ref()
  71             if o is None:
  72                 # This should only happen
  73                 return default
  74             else:
  75                 return o
  76
  77     def items(self):
  78         L = []
  79         for key, ref in self.data.items():
  80             o = ref()
  81             if o is not None:
  82                 L.append((key, o))
  83         return L
  84
  85     def popitem(self):
  86         while 1:
  87             key, ref = self.data.popitem()
  88             o = ref()
  89             if o is not None:
  90                 return key, o
  91
  92     def setdefault(self, key, default):
  93         try:
  94             ref = self.data[key]
  95         except KeyError:
  96             def remove(o, data=self.data, key=key):
  97                 del data[key]
  98             ref = ref(default, remove)
  99             self.data[key] = ref
 100             return default
 101         else:
 102             return ref()
 103
 104     def update(self, dict):
 105         d = self.data
 106         L = []
 107         for key, o in dict.items():
 108             def remove(o, data=d, key=key):
 109                 del data[key]
 110             L.append(key, ref(o, remove))
 111         for key, r in L:
 112             d[key] = r
 113
 114     def values(self):
 115         L = []
 116         for ref in self.data.values():
 117             o = ref()
 118             if o is not None:
 119                 L.append(o)
 120         return L
 121
 122
 123 class WeakKeyDictionary(UserDict.UserDict):
 124
 125     def __init__(self, dict=None):
 126         self.data = {}
 127         if dict is not None: self.update(dict)
 128         def remove(k, data=self.data):
 129             del data[k]
 130         self._remove = remove
 131
 132     def __getitem__(self, key):
 133         return self.data[ref(key)]
 134
 135     def __repr__(self):
 136         return "<WeakKeyDictionary at %s>" % id(self)
 137
 138     def __setitem__(self, key, value):
 139         self.data[ref(key, self._remove)] = value
 140
 141     def copy(self):
 142         new = WeakKeyDictionary()
 143         for key, value in self.data.items():
 144             o = key()
 145             if o is not None:
 146                 new[o] = value
 147         return new
 148
 149     def get(self, key, default):
 150         return self.data.get(ref(key),default)
 151
 152     def items(self):
 153         L = []
 154         for key, value in self.data.items():
 155             o = key()
 156             if o is not None:
 157                 L.append((o, value))
 158         return L
 159
 160     def popitem(self):
 161         while 1:
 162             key, value = self.data.popitem()
 163             o = key()
 164             if o is not None:
 165                 return o, value
 166
 167     def setdefault(self, key, default):
 168         return self.data.setdefault(ref(key, self._remove),default)
 169
 170     def update(self, dict):
 171         d = self.data
 172         L = []
 173         for key, value in dict.items():
 174             L.append(ref(key, self._remove), value)
 175         for key, r in L:
 176             d[key] = r
 177
 178 # no longer needed
 179 del UserDict