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42a139ed88
Deprecated passing the following arguments as keyword arguments: - "func" in functools.partialmethod(), weakref.finalize(), profile.Profile.runcall(), cProfile.Profile.runcall(), bdb.Bdb.runcall(), trace.Trace.runfunc() and curses.wrapper(). - "function" in unittest.addModuleCleanup() and unittest.TestCase.addCleanup(). - "fn" in the submit() method of concurrent.futures.ThreadPoolExecutor and concurrent.futures.ProcessPoolExecutor. - "callback" in contextlib.ExitStack.callback(), contextlib.AsyncExitStack.callback() and contextlib.AsyncExitStack.push_async_callback(). - "c" and "typeid" in the create() method of multiprocessing.managers.Server and multiprocessing.managers.SharedMemoryServer. - "obj" in weakref.finalize(). Also allowed to pass arbitrary keyword arguments (even "self" and "func") if the above arguments are passed as positional argument.
663 lines
21 KiB
Python
663 lines
21 KiB
Python
"""Weak reference support for Python.
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This module is an implementation of PEP 205:
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http://www.python.org/dev/peps/pep-0205/
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"""
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# Naming convention: Variables named "wr" are weak reference objects;
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# they are called this instead of "ref" to avoid name collisions with
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# the module-global ref() function imported from _weakref.
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from _weakref import (
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getweakrefcount,
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getweakrefs,
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ref,
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proxy,
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CallableProxyType,
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ProxyType,
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ReferenceType,
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_remove_dead_weakref)
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from _weakrefset import WeakSet, _IterationGuard
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import _collections_abc # Import after _weakref to avoid circular import.
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import sys
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import itertools
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ProxyTypes = (ProxyType, CallableProxyType)
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__all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
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"WeakKeyDictionary", "ReferenceType", "ProxyType",
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"CallableProxyType", "ProxyTypes", "WeakValueDictionary",
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"WeakSet", "WeakMethod", "finalize"]
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class WeakMethod(ref):
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"""
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A custom `weakref.ref` subclass which simulates a weak reference to
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a bound method, working around the lifetime problem of bound methods.
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"""
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__slots__ = "_func_ref", "_meth_type", "_alive", "__weakref__"
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def __new__(cls, meth, callback=None):
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try:
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obj = meth.__self__
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func = meth.__func__
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except AttributeError:
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raise TypeError("argument should be a bound method, not {}"
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.format(type(meth))) from None
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def _cb(arg):
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# The self-weakref trick is needed to avoid creating a reference
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# cycle.
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self = self_wr()
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if self._alive:
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self._alive = False
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if callback is not None:
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callback(self)
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self = ref.__new__(cls, obj, _cb)
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self._func_ref = ref(func, _cb)
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self._meth_type = type(meth)
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self._alive = True
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self_wr = ref(self)
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return self
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def __call__(self):
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obj = super().__call__()
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func = self._func_ref()
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if obj is None or func is None:
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return None
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return self._meth_type(func, obj)
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def __eq__(self, other):
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if isinstance(other, WeakMethod):
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if not self._alive or not other._alive:
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return self is other
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return ref.__eq__(self, other) and self._func_ref == other._func_ref
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return False
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def __ne__(self, other):
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if isinstance(other, WeakMethod):
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if not self._alive or not other._alive:
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return self is not other
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return ref.__ne__(self, other) or self._func_ref != other._func_ref
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return True
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__hash__ = ref.__hash__
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class WeakValueDictionary(_collections_abc.MutableMapping):
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"""Mapping class that references values weakly.
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Entries in the dictionary will be discarded when no strong
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reference to the value exists anymore
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"""
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# We inherit the constructor without worrying about the input
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# dictionary; since it uses our .update() method, we get the right
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# checks (if the other dictionary is a WeakValueDictionary,
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# objects are unwrapped on the way out, and we always wrap on the
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# way in).
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def __init__(*args, **kw):
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if not args:
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raise TypeError("descriptor '__init__' of 'WeakValueDictionary' "
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"object needs an argument")
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self, *args = args
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if len(args) > 1:
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raise TypeError('expected at most 1 arguments, got %d' % len(args))
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def remove(wr, selfref=ref(self), _atomic_removal=_remove_dead_weakref):
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self = selfref()
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if self is not None:
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if self._iterating:
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self._pending_removals.append(wr.key)
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else:
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# Atomic removal is necessary since this function
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# can be called asynchronously by the GC
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_atomic_removal(d, wr.key)
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self._remove = remove
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# A list of keys to be removed
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self._pending_removals = []
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self._iterating = set()
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self.data = d = {}
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self.update(*args, **kw)
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def _commit_removals(self):
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l = self._pending_removals
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d = self.data
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# We shouldn't encounter any KeyError, because this method should
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# always be called *before* mutating the dict.
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while l:
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key = l.pop()
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_remove_dead_weakref(d, key)
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def __getitem__(self, key):
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if self._pending_removals:
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self._commit_removals()
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o = self.data[key]()
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if o is None:
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raise KeyError(key)
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else:
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return o
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def __delitem__(self, key):
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if self._pending_removals:
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self._commit_removals()
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del self.data[key]
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def __len__(self):
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if self._pending_removals:
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self._commit_removals()
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return len(self.data)
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def __contains__(self, key):
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if self._pending_removals:
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self._commit_removals()
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try:
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o = self.data[key]()
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except KeyError:
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return False
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return o is not None
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def __repr__(self):
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return "<%s at %#x>" % (self.__class__.__name__, id(self))
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def __setitem__(self, key, value):
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if self._pending_removals:
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self._commit_removals()
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self.data[key] = KeyedRef(value, self._remove, key)
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def copy(self):
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if self._pending_removals:
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self._commit_removals()
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new = WeakValueDictionary()
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with _IterationGuard(self):
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for key, wr in self.data.items():
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o = wr()
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if o is not None:
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new[key] = o
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return new
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__copy__ = copy
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def __deepcopy__(self, memo):
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from copy import deepcopy
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if self._pending_removals:
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self._commit_removals()
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new = self.__class__()
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with _IterationGuard(self):
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for key, wr in self.data.items():
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o = wr()
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if o is not None:
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new[deepcopy(key, memo)] = o
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return new
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def get(self, key, default=None):
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if self._pending_removals:
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self._commit_removals()
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try:
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wr = self.data[key]
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except KeyError:
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return default
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else:
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o = wr()
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if o is None:
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# This should only happen
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return default
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else:
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return o
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def items(self):
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if self._pending_removals:
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self._commit_removals()
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with _IterationGuard(self):
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for k, wr in self.data.items():
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v = wr()
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if v is not None:
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yield k, v
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def keys(self):
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if self._pending_removals:
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self._commit_removals()
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with _IterationGuard(self):
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for k, wr in self.data.items():
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if wr() is not None:
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yield k
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__iter__ = keys
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def itervaluerefs(self):
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"""Return an iterator that yields the weak references to the values.
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The references are not guaranteed to be 'live' at the time
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they are used, so the result of calling the references needs
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to be checked before being used. This can be used to avoid
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creating references that will cause the garbage collector to
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keep the values around longer than needed.
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"""
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if self._pending_removals:
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self._commit_removals()
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with _IterationGuard(self):
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yield from self.data.values()
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def values(self):
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if self._pending_removals:
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self._commit_removals()
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with _IterationGuard(self):
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for wr in self.data.values():
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obj = wr()
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if obj is not None:
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yield obj
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def popitem(self):
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if self._pending_removals:
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self._commit_removals()
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while True:
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key, wr = self.data.popitem()
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o = wr()
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if o is not None:
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return key, o
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def pop(self, key, *args):
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if self._pending_removals:
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self._commit_removals()
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try:
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o = self.data.pop(key)()
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except KeyError:
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o = None
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if o is None:
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if args:
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return args[0]
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else:
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raise KeyError(key)
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else:
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return o
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def setdefault(self, key, default=None):
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try:
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o = self.data[key]()
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except KeyError:
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o = None
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if o is None:
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if self._pending_removals:
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self._commit_removals()
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self.data[key] = KeyedRef(default, self._remove, key)
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return default
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else:
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return o
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def update(*args, **kwargs):
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if not args:
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raise TypeError("descriptor 'update' of 'WeakValueDictionary' "
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"object needs an argument")
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self, *args = args
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if len(args) > 1:
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raise TypeError('expected at most 1 arguments, got %d' % len(args))
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dict = args[0] if args else None
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if self._pending_removals:
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self._commit_removals()
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d = self.data
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if dict is not None:
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if not hasattr(dict, "items"):
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dict = type({})(dict)
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for key, o in dict.items():
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d[key] = KeyedRef(o, self._remove, key)
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if len(kwargs):
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self.update(kwargs)
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def valuerefs(self):
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"""Return a list of weak references to the values.
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The references are not guaranteed to be 'live' at the time
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they are used, so the result of calling the references needs
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to be checked before being used. This can be used to avoid
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creating references that will cause the garbage collector to
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keep the values around longer than needed.
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"""
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if self._pending_removals:
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self._commit_removals()
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return list(self.data.values())
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class KeyedRef(ref):
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"""Specialized reference that includes a key corresponding to the value.
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This is used in the WeakValueDictionary to avoid having to create
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a function object for each key stored in the mapping. A shared
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callback object can use the 'key' attribute of a KeyedRef instead
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of getting a reference to the key from an enclosing scope.
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"""
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__slots__ = "key",
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def __new__(type, ob, callback, key):
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self = ref.__new__(type, ob, callback)
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self.key = key
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return self
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def __init__(self, ob, callback, key):
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super().__init__(ob, callback)
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class WeakKeyDictionary(_collections_abc.MutableMapping):
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""" Mapping class that references keys weakly.
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Entries in the dictionary will be discarded when there is no
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longer a strong reference to the key. This can be used to
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associate additional data with an object owned by other parts of
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an application without adding attributes to those objects. This
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can be especially useful with objects that override attribute
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accesses.
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"""
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def __init__(self, dict=None):
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self.data = {}
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def remove(k, selfref=ref(self)):
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self = selfref()
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if self is not None:
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if self._iterating:
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self._pending_removals.append(k)
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else:
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del self.data[k]
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self._remove = remove
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# A list of dead weakrefs (keys to be removed)
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self._pending_removals = []
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self._iterating = set()
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self._dirty_len = False
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if dict is not None:
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self.update(dict)
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def _commit_removals(self):
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# NOTE: We don't need to call this method before mutating the dict,
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# because a dead weakref never compares equal to a live weakref,
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# even if they happened to refer to equal objects.
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# However, it means keys may already have been removed.
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l = self._pending_removals
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d = self.data
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while l:
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try:
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del d[l.pop()]
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except KeyError:
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pass
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def _scrub_removals(self):
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d = self.data
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self._pending_removals = [k for k in self._pending_removals if k in d]
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self._dirty_len = False
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def __delitem__(self, key):
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self._dirty_len = True
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del self.data[ref(key)]
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def __getitem__(self, key):
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return self.data[ref(key)]
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def __len__(self):
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if self._dirty_len and self._pending_removals:
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# self._pending_removals may still contain keys which were
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# explicitly removed, we have to scrub them (see issue #21173).
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self._scrub_removals()
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return len(self.data) - len(self._pending_removals)
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def __repr__(self):
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return "<%s at %#x>" % (self.__class__.__name__, id(self))
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def __setitem__(self, key, value):
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self.data[ref(key, self._remove)] = value
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def copy(self):
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new = WeakKeyDictionary()
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with _IterationGuard(self):
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for key, value in self.data.items():
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o = key()
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if o is not None:
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new[o] = value
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return new
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__copy__ = copy
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def __deepcopy__(self, memo):
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from copy import deepcopy
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new = self.__class__()
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with _IterationGuard(self):
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for key, value in self.data.items():
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o = key()
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if o is not None:
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new[o] = deepcopy(value, memo)
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return new
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def get(self, key, default=None):
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return self.data.get(ref(key),default)
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def __contains__(self, key):
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try:
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wr = ref(key)
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except TypeError:
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return False
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return wr in self.data
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def items(self):
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with _IterationGuard(self):
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for wr, value in self.data.items():
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key = wr()
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if key is not None:
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yield key, value
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def keys(self):
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with _IterationGuard(self):
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for wr in self.data:
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obj = wr()
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if obj is not None:
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yield obj
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__iter__ = keys
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def values(self):
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with _IterationGuard(self):
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for wr, value in self.data.items():
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if wr() is not None:
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yield value
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def keyrefs(self):
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"""Return a list of weak references to the keys.
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The references are not guaranteed to be 'live' at the time
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they are used, so the result of calling the references needs
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to be checked before being used. This can be used to avoid
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creating references that will cause the garbage collector to
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keep the keys around longer than needed.
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"""
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return list(self.data)
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def popitem(self):
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self._dirty_len = True
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while True:
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key, value = self.data.popitem()
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o = key()
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if o is not None:
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return o, value
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def pop(self, key, *args):
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self._dirty_len = True
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return self.data.pop(ref(key), *args)
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def setdefault(self, key, default=None):
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return self.data.setdefault(ref(key, self._remove),default)
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def update(self, dict=None, **kwargs):
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d = self.data
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if dict is not None:
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if not hasattr(dict, "items"):
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dict = type({})(dict)
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for key, value in dict.items():
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d[ref(key, self._remove)] = value
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if len(kwargs):
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self.update(kwargs)
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class finalize:
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"""Class for finalization of weakrefable objects
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finalize(obj, func, *args, **kwargs) returns a callable finalizer
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object which will be called when obj is garbage collected. The
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first time the finalizer is called it evaluates func(*arg, **kwargs)
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and returns the result. After this the finalizer is dead, and
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calling it just returns None.
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When the program exits any remaining finalizers for which the
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atexit attribute is true will be run in reverse order of creation.
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By default atexit is true.
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"""
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# Finalizer objects don't have any state of their own. They are
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# just used as keys to lookup _Info objects in the registry. This
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# ensures that they cannot be part of a ref-cycle.
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__slots__ = ()
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_registry = {}
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_shutdown = False
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_index_iter = itertools.count()
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_dirty = False
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_registered_with_atexit = False
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class _Info:
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__slots__ = ("weakref", "func", "args", "kwargs", "atexit", "index")
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def __init__(*args, **kwargs):
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if len(args) >= 3:
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self, obj, func, *args = args
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elif not args:
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raise TypeError("descriptor '__init__' of 'finalize' object "
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"needs an argument")
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else:
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if 'func' not in kwargs:
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raise TypeError('finalize expected at least 2 positional '
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'arguments, got %d' % (len(args)-1))
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func = kwargs.pop('func')
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if len(args) >= 2:
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self, obj, *args = args
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import warnings
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warnings.warn("Passing 'func' as keyword argument is deprecated",
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|
DeprecationWarning, stacklevel=2)
|
|
else:
|
|
if 'obj' not in kwargs:
|
|
raise TypeError('finalize expected at least 2 positional '
|
|
'arguments, got %d' % (len(args)-1))
|
|
obj = kwargs.pop('obj')
|
|
self, *args = args
|
|
import warnings
|
|
warnings.warn("Passing 'obj' as keyword argument is deprecated",
|
|
DeprecationWarning, stacklevel=2)
|
|
args = tuple(args)
|
|
|
|
if not self._registered_with_atexit:
|
|
# We may register the exit function more than once because
|
|
# of a thread race, but that is harmless
|
|
import atexit
|
|
atexit.register(self._exitfunc)
|
|
finalize._registered_with_atexit = True
|
|
info = self._Info()
|
|
info.weakref = ref(obj, self)
|
|
info.func = func
|
|
info.args = args
|
|
info.kwargs = kwargs or None
|
|
info.atexit = True
|
|
info.index = next(self._index_iter)
|
|
self._registry[self] = info
|
|
finalize._dirty = True
|
|
|
|
def __call__(self, _=None):
|
|
"""If alive then mark as dead and return func(*args, **kwargs);
|
|
otherwise return None"""
|
|
info = self._registry.pop(self, None)
|
|
if info and not self._shutdown:
|
|
return info.func(*info.args, **(info.kwargs or {}))
|
|
|
|
def detach(self):
|
|
"""If alive then mark as dead and return (obj, func, args, kwargs);
|
|
otherwise return None"""
|
|
info = self._registry.get(self)
|
|
obj = info and info.weakref()
|
|
if obj is not None and self._registry.pop(self, None):
|
|
return (obj, info.func, info.args, info.kwargs or {})
|
|
|
|
def peek(self):
|
|
"""If alive then return (obj, func, args, kwargs);
|
|
otherwise return None"""
|
|
info = self._registry.get(self)
|
|
obj = info and info.weakref()
|
|
if obj is not None:
|
|
return (obj, info.func, info.args, info.kwargs or {})
|
|
|
|
@property
|
|
def alive(self):
|
|
"""Whether finalizer is alive"""
|
|
return self in self._registry
|
|
|
|
@property
|
|
def atexit(self):
|
|
"""Whether finalizer should be called at exit"""
|
|
info = self._registry.get(self)
|
|
return bool(info) and info.atexit
|
|
|
|
@atexit.setter
|
|
def atexit(self, value):
|
|
info = self._registry.get(self)
|
|
if info:
|
|
info.atexit = bool(value)
|
|
|
|
def __repr__(self):
|
|
info = self._registry.get(self)
|
|
obj = info and info.weakref()
|
|
if obj is None:
|
|
return '<%s object at %#x; dead>' % (type(self).__name__, id(self))
|
|
else:
|
|
return '<%s object at %#x; for %r at %#x>' % \
|
|
(type(self).__name__, id(self), type(obj).__name__, id(obj))
|
|
|
|
@classmethod
|
|
def _select_for_exit(cls):
|
|
# Return live finalizers marked for exit, oldest first
|
|
L = [(f,i) for (f,i) in cls._registry.items() if i.atexit]
|
|
L.sort(key=lambda item:item[1].index)
|
|
return [f for (f,i) in L]
|
|
|
|
@classmethod
|
|
def _exitfunc(cls):
|
|
# At shutdown invoke finalizers for which atexit is true.
|
|
# This is called once all other non-daemonic threads have been
|
|
# joined.
|
|
reenable_gc = False
|
|
try:
|
|
if cls._registry:
|
|
import gc
|
|
if gc.isenabled():
|
|
reenable_gc = True
|
|
gc.disable()
|
|
pending = None
|
|
while True:
|
|
if pending is None or finalize._dirty:
|
|
pending = cls._select_for_exit()
|
|
finalize._dirty = False
|
|
if not pending:
|
|
break
|
|
f = pending.pop()
|
|
try:
|
|
# gc is disabled, so (assuming no daemonic
|
|
# threads) the following is the only line in
|
|
# this function which might trigger creation
|
|
# of a new finalizer
|
|
f()
|
|
except Exception:
|
|
sys.excepthook(*sys.exc_info())
|
|
assert f not in cls._registry
|
|
finally:
|
|
# prevent any more finalizers from executing during shutdown
|
|
finalize._shutdown = True
|
|
if reenable_gc:
|
|
gc.enable()
|