Python weakref.ref() Examples

def test_task_refcounting(self):
        # On CPython, tasks and their arguments should be released immediately
        # without waiting for garbage collection.
        @gen.engine
        def f():
            class Foo(object):
                pass
            arg = Foo()
            self.arg_ref = weakref.ref(arg)
            task = gen.Task(self.io_loop.add_callback, arg=arg)
            self.task_ref = weakref.ref(task)
            yield task
            self.stop()

        self.run_gen(f)
        self.assertIs(self.arg_ref(), None)
        self.assertIs(self.task_ref(), None) 

def _start_queue_management_thread(self):
        # When the executor gets lost, the weakref callback will wake up
        # the queue management thread.
        def weakref_cb(_, q=self._result_queue):
            q.put(None)
        if self._queue_management_thread is None:
            self._queue_management_thread = threading.Thread(
                    target=_queue_management_worker,
                    args=(weakref.ref(self, weakref_cb),
                          self._processes,
                          self._pending_work_items,
                          self._work_ids,
                          self._call_queue,
                          self._result_queue))
            self._queue_management_thread.daemon = True
            self._queue_management_thread.start()
            _threads_queues[self._queue_management_thread] = self._result_queue 

def create_dict(self):
        """Create a new dict for the current thread, and return it."""
        localdict = {}
        key = self.key
        thread = current_thread()
        idt = id(thread)
        def local_deleted(_, key=key):
            # When the localimpl is deleted, remove the thread attribute.
            thread = wrthread()
            if thread is not None:
                del thread.__dict__[key]
        def thread_deleted(_, idt=idt):
            # When the thread is deleted, remove the local dict.
            # Note that this is suboptimal if the thread object gets
            # caught in a reference loop. We would like to be called
            # as soon as the OS-level thread ends instead.
            local = wrlocal()
            if local is not None:
                dct = local.dicts.pop(idt)
        wrlocal = ref(self, local_deleted)
        wrthread = ref(thread, thread_deleted)
        thread.__dict__[key] = wrlocal
        self.dicts[idt] = wrthread, localdict
        return localdict 

def subscribe(func):
    '''
    Add a subscriber function to option events

    Parameters
    ----------
    func : callable
        A callable object that takes two parameters: key and value.
        This function is called with the name and value of any option
        that is set.

    Returns
    -------
    None

    '''
    if isinstance(func, types.MethodType):
        obj = six.get_method_self(func)
        func = six.get_method_function(func)
        _subscribers[func] = (weakref.ref(func), weakref.ref(obj))
    else:
        _subscribers[func] = (weakref.ref(func), None) 

def ensure_proc_terminate(proc):
    """
    Make sure processes terminate when main process exit.

    Args:
        proc (multiprocessing.Process or list)
    """
    if isinstance(proc, list):
        for p in proc:
            ensure_proc_terminate(p)
        return

    def stop_proc_by_weak_ref(ref):
        proc = ref()
        if proc is None:
            return
        if not proc.is_alive():
            return
        proc.terminate()
        proc.join()

    assert isinstance(proc, mp.Process)
    atexit.register(stop_proc_by_weak_ref, weakref.ref(proc)) 

def _adjust_thread_count(self):
        # When the executor gets lost, the weakref callback will wake up
        # the worker threads.
        def weakref_cb(_, q=self._work_queue):
            q.put(None)
        # TODO(bquinlan): Should avoid creating new threads if there are more
        # idle threads than items in the work queue.
        num_threads = len(self._threads)
        if num_threads < self._max_workers:
            thread_name = '%s_%d' % (self._thread_name_prefix or self,
                                     num_threads)
            t = threading.Thread(name=thread_name, target=_worker,
                                 args=(weakref.ref(self, weakref_cb),
                                       self._work_queue))
            t.daemon = True
            t.start()
            self._threads.add(t)
            _threads_queues[t] = self._work_queue 

def _start_queue_management_thread(self):
        # When the executor gets lost, the weakref callback will wake up
        # the queue management thread.
        def weakref_cb(_, q=self._result_queue):
            q.put(None)
        if self._queue_management_thread is None:
            self._queue_management_thread = threading.Thread(
                    target=_queue_management_worker,
                    args=(weakref.ref(self, weakref_cb),
                          self._processes,
                          self._pending_work_items,
                          self._work_ids,
                          self._call_queue,
                          self._result_queue))
            self._queue_management_thread.daemon = True
            self._queue_management_thread.start()
            _threads_queues[self._queue_management_thread] = self._result_queue 

def lex(self, source, name=None, filename=None):
        """Lex the given sourcecode and return a generator that yields
        tokens as tuples in the form ``(lineno, token_type, value)``.
        This can be useful for :ref:`extension development <writing-extensions>`
        and debugging templates.

        This does not perform preprocessing.  If you want the preprocessing
        of the extensions to be applied you have to filter source through
        the :meth:`preprocess` method.
        """
        source = text_type(source)
        try:
            return self.lexer.tokeniter(source, name, filename)
        except TemplateSyntaxError:
            exc_info = sys.exc_info()
        self.handle_exception(exc_info, source_hint=source) 

def test_task_refcounting(self):
        # On CPython, tasks and their arguments should be released immediately
        # without waiting for garbage collection.
        @gen.engine
        def f():
            class Foo(object):
                pass
            arg = Foo()
            self.arg_ref = weakref.ref(arg)
            task = gen.Task(self.io_loop.add_callback, arg=arg)
            self.task_ref = weakref.ref(task)
            yield task
            self.stop()

        self.run_gen(f)
        self.assertIs(self.arg_ref(), None)
        self.assertIs(self.task_ref(), None) 

def _start_queue_management_thread(self):
        # When the executor gets lost, the weakref callback will wake up
        # the queue management thread.
        def weakref_cb(_, q=self._result_queue):
            q.put(None)
        if self._queue_management_thread is None:
            self._queue_management_thread = threading.Thread(
                    target=_queue_management_worker,
                    args=(weakref.ref(self, weakref_cb),
                          self._processes,
                          self._pending_work_items,
                          self._work_ids,
                          self._call_queue,
                          self._result_queue))
            self._queue_management_thread.daemon = True
            self._queue_management_thread.start()
            _threads_queues[self._queue_management_thread] = self._result_queue 

def _adjust_thread_count(self):
        # if idle threads are available, don't spin new threads
        if self._idle_semaphore.acquire(False):
            return

        # When the executor gets lost, the weakref callback will wake up
        # the worker threads.
        def weakref_cb(_, q=self._work_queue):
            q.put(None)

        num_threads = len(self._threads)
        if num_threads < self._max_workers:
            thread_name = '%s_%d' % (self._thread_name_prefix or self,
                                     num_threads)
            t = threading.Thread(name=thread_name, target=_worker,
                                 args=(weakref.ref(self, weakref_cb),
                                       self._work_queue))
            t.daemon = True
            t.start()
            self._threads.add(t)
            _threads_queues[t] = self._work_queue 

def lex(self, source, name=None, filename=None):
        """Lex the given sourcecode and return a generator that yields
        tokens as tuples in the form ``(lineno, token_type, value)``.
        This can be useful for :ref:`extension development <writing-extensions>`
        and debugging templates.

        This does not perform preprocessing.  If you want the preprocessing
        of the extensions to be applied you have to filter source through
        the :meth:`preprocess` method.
        """
        source = text_type(source)
        try:
            return self.lexer.tokeniter(source, name, filename)
        except TemplateSyntaxError:
            exc_info = sys.exc_info()
        self.handle_exception(exc_info, source_hint=source) 

def lex(self, source, name=None, filename=None):
        """Lex the given sourcecode and return a generator that yields
        tokens as tuples in the form ``(lineno, token_type, value)``.
        This can be useful for :ref:`extension development <writing-extensions>`
        and debugging templates.

        This does not perform preprocessing.  If you want the preprocessing
        of the extensions to be applied you have to filter source through
        the :meth:`preprocess` method.
        """
        source = text_type(source)
        try:
            return self.lexer.tokeniter(source, name, filename)
        except TemplateSyntaxError:
            exc_info = sys.exc_info()
        self.handle_exception(exc_info, source_hint=source) 

def __init__(self, obj, func, *args, **kwargs):
        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 on_switch(self, old_tab: QWidget) -> None:
        """Record tab switch events."""
        if self._ignore_next:
            self._ignore_next = False
            self._keep_deleted_next = False
            return
        tab = weakref.ref(old_tab)
        if self._stack_deleted and not self._keep_deleted_next:
            self._stack_deleted = []
        self._keep_deleted_next = False
        self._stack.append(tab) 

def _set_request_state(self, sock_info):
        ident = self._ident
        tid = ident.get()

        if sock_info == NO_REQUEST:
            # Ending a request
            ident.unwatch(tid)
            self._tid_to_sock.pop(tid, None)
        else:
            self._tid_to_sock[tid] = sock_info

            if not ident.watching():
                # Closure over tid, poolref, and ident. Don't refer directly to
                # self, otherwise there's a cycle.

                # Do not access threadlocals in this function, or any
                # function it calls! In the case of the Pool subclass and
                # mod_wsgi 2.x, on_thread_died() is triggered when mod_wsgi
                # calls PyThreadState_Clear(), which deferences the
                # ThreadVigil and triggers the weakref callback. Accessing
                # thread locals in this function, while PyThreadState_Clear()
                # is in progress can cause leaks, see PYTHON-353.
                poolref = weakref.ref(self)

                def on_thread_died(ref):
                    try:
                        ident.unwatch(tid)
                        pool = poolref()
                        if pool:
                            # End the request
                            request_sock = pool._tid_to_sock.pop(tid, None)

                            # Was thread ever assigned a socket before it died?
                            if request_sock not in (NO_REQUEST, NO_SOCKET_YET):
                                pool._return_socket(request_sock)
                    except:
                        # Random exceptions on interpreter shutdown.
                        pass

                ident.watch(on_thread_died) 

def __init__(self, connection):
        """Instantiate the manager.

        :Parameters:
          - `connection`: a Mongo Connection
        """
        self.__dying_cursors = []
        self.__max_dying_cursors = 20
        self.__connection = weakref.ref(connection)

        CursorManager.__init__(self, connection) 

def register_monitor(monitor):
    ref = weakref.ref(monitor, _on_monitor_deleted)
    MONITORS.add(ref) 

def watch(self, callback):
        vigil = self._make_vigil()
        self._refs[id(vigil)] = weakref.ref(vigil, callback) 

def watch(self, callback):
        current = greenlet.getcurrent()
        tid = self.get()

        if hasattr(current, 'link'):
            # This is a Gevent Greenlet (capital G), which inherits from
            # greenlet and provides a 'link' method to detect when the
            # Greenlet exits.
            link = SpawnedLink(callback)
            current.rawlink(link)
            self._refs[tid] = link
        else:
            # This is a non-Gevent greenlet (small g), or it's the main
            # greenlet.
            self._refs[tid] = weakref.ref(current, callback) 

def shutdown_monitors():
    # Keep a local copy of MONITORS as
    # shutting down threads has a side effect
    # of removing them from the MONITORS set()
    monitors = list(MONITORS)
    for ref in monitors:
        monitor = ref()
        if monitor:
            monitor.shutdown()
            monitor.join(10) 

def _notify_registry(height: int = None) -> None:
    gc.collect()
    if height is None:
        height = web3.eth.blockNumber
    for ref in _revert_refs.copy():
        obj = ref()
        if obj is None:
            _revert_refs.remove(ref)
        elif height:
            obj._revert(height)
        else:
            obj._reset() 

def _revert_register(obj: object) -> None:
    _revert_refs.append(weakref.ref(obj)) 

def prev(self, cur_tab: QWidget) -> QWidget:
        """Get the 'previous' tab in the stack.

        Throws IndexError on failure.
        """
        tab = None  # type: typing.Optional[QWidget]
        while tab is None or tab.pending_removal or tab is cur_tab:
            tab = self._stack.pop()()
        self._stack_deleted.append(weakref.ref(cur_tab))
        self._ignore_next = True
        return tab 

def parse(self, source, name=None, filename=None):
        """Parse the sourcecode and return the abstract syntax tree.  This
        tree of nodes is used by the compiler to convert the template into
        executable source- or bytecode.  This is useful for debugging or to
        extract information from templates.

        If you are :ref:`developing Jinja2 extensions <writing-extensions>`
        this gives you a good overview of the node tree generated.
        """
        try:
            return self._parse(source, name, filename)
        except TemplateSyntaxError:
            exc_info = sys.exc_info()
        self.handle_exception(exc_info, source_hint=source) 

def _adjust_thread_count(self):
        # When the executor gets lost, the weakref callback will wake up
        # the worker threads.
        def weakref_cb(_, q=self._work_queue):
            q.put(None)
        # TODO(bquinlan): Should avoid creating new threads if there are more
        # idle threads than items in the work queue.
        if len(self._threads) < self._max_workers:
            t = threading.Thread(target=_worker,
                                 args=(weakref.ref(self, weakref_cb),
                                       self._work_queue))
            t.daemon = True
            t.start()
            self._threads.add(t)
            _threads_queues[t] = self._work_queue 

def _load_template(self, name, globals):
        if self.loader is None:
            raise TypeError('no loader for this environment specified')
        cache_key = (weakref.ref(self.loader), name)
        if self.cache is not None:
            template = self.cache.get(cache_key)
            if template is not None and (not self.auto_reload or
                                         template.is_up_to_date):
                return template
        template = self.loader.load(self, name, globals)
        if self.cache is not None:
            self.cache[cache_key] = template
        return template 

def extend(self, **attributes):
        """Add the items to the instance of the environment if they do not exist
        yet.  This is used by :ref:`extensions <writing-extensions>` to register
        callbacks and configuration values without breaking inheritance.
        """
        for key, value in iteritems(attributes):
            if not hasattr(self, key):
                setattr(self, key, value) 

def _load_template(self, name, globals):
        if self.loader is None:
            raise TypeError('no loader for this environment specified')
        cache_key = (weakref.ref(self.loader), name)
        if self.cache is not None:
            template = self.cache.get(cache_key)
            if template is not None and (not self.auto_reload or
                                         template.is_up_to_date):
                return template
        template = self.loader.load(self, name, globals)
        if self.cache is not None:
            self.cache[cache_key] = template
        return template 

def __init__(self, projectdb):
            self.get_projectdb = weakref.ref(projectdb)