138 lines
4.6 KiB
Python
138 lines
4.6 KiB
Python
"""Weak reference support for Python.
|
|
|
|
This module is an implementation of PEP 205:
|
|
|
|
http://www.python.org/dev/peps/pep-0205/
|
|
"""
|
|
|
|
# Changed for Jython to use MapMaker in Google Collections
|
|
|
|
# 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.
|
|
|
|
from _weakref import (
|
|
getweakrefcount,
|
|
getweakrefs,
|
|
ref,
|
|
proxy,
|
|
CallableProxyType,
|
|
ProxyType,
|
|
ReferenceType)
|
|
|
|
from _weakrefset import WeakSet
|
|
|
|
from exceptions import ReferenceError
|
|
from jythonlib import MapMaker, dict_builder
|
|
|
|
|
|
ProxyTypes = (ProxyType, CallableProxyType)
|
|
|
|
__all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
|
|
"WeakKeyDictionary", "ReferenceError", "ReferenceType", "ProxyType",
|
|
"CallableProxyType", "ProxyTypes", "WeakValueDictionary", 'WeakSet']
|
|
|
|
|
|
class WeakValueDictionary(dict):
|
|
"""Mapping class that references values weakly.
|
|
|
|
Entries in the dictionary will be discarded when no strong
|
|
reference to the value exists anymore
|
|
"""
|
|
|
|
def __new__(cls, *args, **kw):
|
|
return WeakValueDictionaryBuilder(*args, **kw)
|
|
|
|
def itervaluerefs(self):
|
|
"""Return an iterator that yields the weak references to the values.
|
|
|
|
The references are not guaranteed to be 'live' at the time
|
|
they are used, so the result of calling the references needs
|
|
to be checked before being used. This can be used to avoid
|
|
creating references that will cause the garbage collector to
|
|
keep the values around longer than needed.
|
|
|
|
"""
|
|
for value in self.itervalues():
|
|
yield ref(value)
|
|
|
|
def valuerefs(self):
|
|
"""Return a list of weak references to the values.
|
|
|
|
The references are not guaranteed to be 'live' at the time
|
|
they are used, so the result of calling the references needs
|
|
to be checked before being used. This can be used to avoid
|
|
creating references that will cause the garbage collector to
|
|
keep the values around longer than needed.
|
|
|
|
"""
|
|
return [ref(value) for value in self.itervalues()]
|
|
|
|
WeakValueDictionaryBuilder = dict_builder(MapMaker().weakValues().makeMap, WeakValueDictionary)
|
|
|
|
|
|
class WeakKeyDictionary(dict):
|
|
""" 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 __new__(cls, *args, **kw):
|
|
return WeakKeyDictionaryBuilder(*args, **kw)
|
|
|
|
def iterkeyrefs(self):
|
|
"""Return an iterator that yields the weak references to the keys.
|
|
|
|
The references are not guaranteed to be 'live' at the time
|
|
they are used, so the result of calling the references needs
|
|
to be checked before being used. This can be used to avoid
|
|
creating references that will cause the garbage collector to
|
|
keep the keys around longer than needed.
|
|
|
|
"""
|
|
for key in self.iterkeys():
|
|
yield ref(key)
|
|
|
|
def keyrefs(self):
|
|
"""Return a list of weak references to the keys.
|
|
|
|
The references are not guaranteed to be 'live' at the time
|
|
they are used, so the result of calling the references needs
|
|
to be checked before being used. This can be used to avoid
|
|
creating references that will cause the garbage collector to
|
|
keep the keys around longer than needed.
|
|
|
|
"""
|
|
return [ref(key) for key in self.iterkeys()]
|
|
|
|
WeakKeyDictionaryBuilder = dict_builder(MapMaker().weakKeys().makeMap, WeakKeyDictionary)
|
|
|
|
|
|
# Jython does not use below, however retaining in the case of any user code that might
|
|
# be using it. Note that it is not exported.
|
|
|
|
class KeyedRef(ref):
|
|
"""Specialized reference that includes a key corresponding to the value.
|
|
|
|
This is used in the WeakValueDictionary to avoid having to create
|
|
a function object for each key stored in the mapping. A shared
|
|
callback object can use the 'key' attribute of a KeyedRef instead
|
|
of getting a reference to the key from an enclosing scope.
|
|
|
|
"""
|
|
|
|
__slots__ = "key",
|
|
|
|
def __new__(type, ob, callback, key):
|
|
self = ref.__new__(type, ob, callback)
|
|
self.key = key
|
|
return self
|
|
|
|
def __init__(self, ob, callback, key):
|
|
super(KeyedRef, self).__init__(ob, callback)
|