weakref. If there is no callback or if the referent of the weakref is
no longer alive then this attribute will have value ``None``.
- .. note::
-
- Like :meth:`__del__` methods, weak reference callbacks can be
- called during interpreter shutdown when module globals have been
- overwritten with :const:`None`. This can make writing robust
- weak reference callbacks a challenge. Callbacks registered
- using :class:`finalize` do not have to worry about this issue
- because they will not be run after module teardown has begun.
-
.. versionchanged:: 3.4
Added the :attr:`__callback__` attribute.
.. class:: finalize(obj, func, *args, **kwargs)
Return a callable finalizer object which will be called when *obj*
- is garbage collected. Unlike an ordinary weak reference, a finalizer is
+ is garbage collected. Unlike an ordinary weak reference, a finalizer
will always survive until the reference object is collected, greatly
simplifying lifecycle management.
gc
--
-New :func:`~gc.get_stats` returns a list of three per-generation dictionaries
-containing the collections statistics since interpreter startup. (Contributed
-by Antoine Pitrou in :issue:`16351`.)
+New function :func:`~gc.get_stats` returns a list of three per-generation
+dictionaries containing the collections statistics since interpreter startup.
+(Contributed by Antoine Pitrou in :issue:`16351`.)
hashlib
carefully manage the lifecycle of the weak reference itself. (Contributed by
Richard Oudkerk in :issue:`15528`)
+The callback, if any, associated with a :class:`~weakref.ref` is now
+exposed via the :attr:`~weakref.ref.__callback__` attribute. (Contributed
+by Mark Dickinson in :issue:`17643`.)
+
xml.etree
---------
compliance with the language spec; Jython and PyPy already were.
(:issue:`17434`).
+* :meth:`ssl.SSLSocket.getpeercert` and :meth:`ssl.SSLSocket.do_handshake`
+ now raise an :exc:`OSError` with ``ENOTCONN`` when the ``SSLSocket`` is not
+ connected, instead of the previous behavior of raising an
+ :exc:`AttributError`. In addition, :meth:`~ssl.SSLSocket.getpeercert`
+ will raise a :exc:`ValueError` if the handshake has not yet been done.
+
Changes in the C API
--------------------