diff options
Diffstat (limited to 'Lib')
| -rw-r--r-- | Lib/weakref.py | 60 |
1 files changed, 36 insertions, 24 deletions
diff --git a/Lib/weakref.py b/Lib/weakref.py index b6b4528..32c11ab 100644 --- a/Lib/weakref.py +++ b/Lib/weakref.py @@ -5,6 +5,10 @@ This module is an implementation of PEP 205: http://python.sourceforge.net/peps/pep-0205.html """ +# Naming convention: Variables named "wr" are weak reference objects; +# they are called this instead of "ref" to avoid name collisions with +# the module-global ref() function imported from _weakref. + import UserDict from _weakref import \ @@ -23,8 +27,13 @@ __all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs", "WeakKeyDictionary", "ReferenceType", "ProxyType", "CallableProxyType", "ProxyTypes", "WeakValueDictionary"] + class WeakValueDictionary(UserDict.UserDict): + """Mapping class that references values weakly. + Entries in the dictionary will be discarded when no strong + reference to the value exists anymore + """ # 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 WeakValueDictionary, @@ -48,19 +57,19 @@ class WeakValueDictionary(UserDict.UserDict): def copy(self): new = WeakValueDictionary() - for key, ref in self.data.items(): - o = ref() + for key, wr in self.data.items(): + o = wr() if o is not None: new[key] = o return new def get(self, key, default=None): try: - ref = self.data[key] + wr = self.data[key] except KeyError: return default else: - o = ref() + o = wr() if o is None: # This should only happen return default @@ -69,51 +78,56 @@ class WeakValueDictionary(UserDict.UserDict): def items(self): L = [] - for key, ref in self.data.items(): - o = ref() + for key, wr in self.data.items(): + o = wr() if o is not None: L.append((key, o)) return L def popitem(self): while 1: - key, ref = self.data.popitem() - o = ref() + key, wr = self.data.popitem() + o = wr() if o is not None: return key, o def setdefault(self, key, default): try: - ref = self.data[key] + wr = self.data[key] except KeyError: def remove(o, data=self.data, key=key): del data[key] - ref = ref(default, remove) - self.data[key] = ref + self.data[key] = ref(default, remove) return default else: - return ref() + return wr() 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 + d[key] = ref(o, remove) def values(self): L = [] - for ref in self.data.values(): - o = ref() + for wr in self.data.values(): + o = wr() if o is not None: L.append(o) return L class WeakKeyDictionary(UserDict.UserDict): + """ Mapping class that references keys weakly. + + Entries in the dictionary will be discarded when there is no + longer a strong reference to the key. This can be used to + associate additional data with an object owned by other parts of + an application without adding attributes to those objects. This + can be especially useful with objects that override attribute + accesses. + """ def __init__(self, dict=None): self.data = {} @@ -155,8 +169,8 @@ class WeakKeyDictionary(UserDict.UserDict): def keys(self): L = [] - for ref in self.data.keys(): - o = ref() + for wr in self.data.keys(): + o = wr() if o is not None: L.append(o) return L @@ -173,11 +187,9 @@ class WeakKeyDictionary(UserDict.UserDict): def update(self, dict): d = self.data - L = [] for key, value in dict.items(): - L.append((ref(key, self._remove), value)) - for key, r in L: - d[key] = r + d[ref(key, self._remove)] = value + # no longer needed del UserDict |