online
  $   ˆl–Ãa¾”d*j"TÚzã@¸Ø”Å£Å„[pÄ¿Â ?÷     """Weak reference support for Python.

This module is an implementation of PEP 205:

https://www.python.org/dev/peps/pep-0205/
"""

# 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,
     _remove_dead_weakref)

from _weakrefset import WeakSet, _IterationGuard

import _collections_abc  # Import after _weakref to avoid circular import.
import sys
import itertools

ProxyTypes = (ProxyType, CallableProxyType)

__all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
           "WeakKeyDictionary", "ReferenceType", "ProxyType",
           "CallableProxyType", "ProxyTypes", "WeakValueDictionary",
           "WeakSet", "WeakMethod", "finalize"]


_collections_abc.Set.register(WeakSet)
_collections_abc.MutableSet.register(WeakSet)

class WeakMethod(ref):
    """
    A custom `weakref.ref` subclass which simulates a weak reference to
    a bound method, working around the lifetime problem of bound methods.
    """

    __slots__ = "_func_ref", "_meth_type", "_alive", "__weakref__"

    def __new__(cls, meth, callback=None):
        try:
            obj = meth.__self__
            func = meth.__func__
        except AttributeError:
            raise TypeError("argument should be a bound method, not {}"
                            .format(type(meth))) from None
        def _cb(arg):
            # The self-weakref trick is needed to avoid creating a reference
            # cycle.
            self = self_wr()
            if self._alive:
                self._alive = False
                if callback is not None:
                    callback(self)
        self = ref.__new__(cls, obj, _cb)
        self._func_ref = ref(func, _cb)
        self._meth_type = type(meth)
        self._alive = True
        self_wr = ref(self)
        return self

    def __call__(self):
        obj = super().__call__()
        func = self._func_ref()
        if obj is None or func is None:
            return None
        return self._meth_type(func, obj)

    def __eq__(self, other):
        if isinstance(other, WeakMethod):
            if not self._alive or not other._alive:
                return self is other
            return ref.__eq__(self, other) and self._func_ref == other._func_ref
        return NotImplemented

    def __ne__(self, other):
        if isinstance(other, WeakMethod):
            if not self._alive or not other._alive:
                return self is not other
            return ref.__ne__(self, other) or self._func_ref != other._func_ref
        return NotImplemented

    __hash__ = ref.__hash__


class WeakValueDictionary(_collections_abc.MutableMapping):
    """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,
    # objects are unwrapped on the way out, and we always wrap on the
    # way in).

    def __init__(self, other=(), /, **kw):
        def remove(wr, selfref=ref(self), _atomic_removal=_remove_dead_weakref):
            self = selfref()
            if self is not None:
                if self._iterating:
                    self._pending_removals.append(wr.key)
                else:
                    # Atomic removal is necessary since this function
                    # can be called asynchronously by the GC
                    _atomic_removal(self.data, wr.key)
        self._remove = remove
        # A list of keys to be removed
        self._pending_removals = []
        self._iterating = set()
        self.data = {}
        self.update(other, **kw)

    def _commi