Skip to content
Back to top

# Source code for gevent.queue

    # Copyright (c) 2009-2012 Denis Bilenko. See LICENSE for details.
    # copyright (c) 2018 gevent
    # cython: auto_pickle=False,embedsignature=True,always_allow_keywords=False
    """
    Synchronized queues.

    The :mod:`gevent.queue` module implements multi-producer, multi-consumer queues
    that work across greenlets, with the API similar to the classes found in the
    standard :mod:`Queue` and :class:`multiprocessing <multiprocessing.Queue>` modules.

    The classes in this module implement the iterator protocol. Iterating
    over a queue means repeatedly calling :meth:`get <Queue.get>` until
    :meth:`get <Queue.get>` returns ``StopIteration`` (specifically that
    class, not an instance or subclass).

        >>> import gevent.queue
        >>> queue = gevent.queue.Queue()
        >>> queue.put(1)
        >>> queue.put(2)
        >>> queue.put(StopIteration)
        >>> for item in queue:
        ...    print(item)
        1
        2

    .. versionchanged:: 1.0
           ``Queue(0)`` now means queue of infinite size, not a channel. A :exc:`DeprecationWarning`
           will be issued with this argument.
    """

    import sys
    from heapq import heappush as _heappush
    from heapq import heappop as _heappop
    from heapq import heapify as _heapify
    import collections

    import queue as __queue__
    # We re-export these exceptions to client modules.
    # But we also want fast access to them from Cython with a cdef,
    # and we do that with the _ definition.
    _Full = Full = __queue__.Full
    _Empty = Empty = __queue__.Empty

    from gevent.timeout import Timeout
    from gevent._hub_local import get_hub_noargs as get_hub
    from gevent.exceptions import InvalidSwitchError

    __all__ = []
    __implements__ = ['Queue', 'PriorityQueue', 'LifoQueue']
    __extensions__ = ['JoinableQueue', 'Channel']
    __imports__ = ['Empty', 'Full']

    __all__.append('SimpleQueue')
    # SimpleQueue is implemented in C and directly allocates locks
    # unaffected by monkey patching. We need the Python version.
    SimpleQueue = __queue__._PySimpleQueue # pylint:disable=no-member

    if hasattr(__queue__, 'ShutDown'): # New in 3.13
        ShutDown = __queue__.ShutDown
        __imports__.append('ShutDown')
    else:
        class ShutDown(Exception):
            """
            gevent extension for Python versions less than 3.13
            """
        __extensions__.append('ShutDown')

    __all__ += (__implements__ + __extensions__ + __imports__)

    # pylint 2.0.dev2 things collections.dequeue.popleft() doesn't return
    # pylint:disable=assignment-from-no-return

    def _safe_remove(deq, item):
        # For when the item may have been removed by
        # Queue._unlock
        try:
            deq.remove(item)
        except ValueError:
            pass

    import gevent._waiter
    locals()['Waiter'] = gevent._waiter.Waiter
    locals()['getcurrent'] = __import__('greenlet').getcurrent
    locals()['greenlet_init'] = lambda: None

    class ItemWaiter(Waiter): # pylint:disable=undefined-variable
        # pylint:disable=assigning-non-slot
        __slots__ = (
            'item',
            'queue',
        )

        def __init__(self, item, queue):
            Waiter.__init__(self) # pylint:disable=undefined-variable
            self.item = item
            self.queue = queue

        def put_and_switch(self):
            self.queue._put(self.item)
            self.queue = None
            self.item = None
            return self.switch(self)

    class Queue(object):
        """
        Create a queue object with a given maximum size.

        If *maxsize* is less than or equal to zero or ``None``, the queue
        size is infinite.

        Queues have a ``len`` equal to the number of items in them (the :meth:`qsize`),
        but in a boolean context they are always True.

        .. versionchanged:: 1.1b3
           Queues now support :func:`len`; it behaves the same as :meth:`qsize`.
        .. versionchanged:: 1.1b3
           Multiple greenlets that block on a call to :meth:`put` for a full queue
           will now be awakened to put their items into the queue in the order in which
           they arrived. Likewise, multiple greenlets that block on a call to :meth:`get` for
           an empty queue will now receive items in the order in which they blocked. An
           implementation quirk under CPython *usually* ensured this was roughly the case
           previously anyway, but that wasn't the case for PyPy.
        .. versionchanged:: 24.10.1
           Implement the ``shutdown`` methods from Python 3.13.
        """

        __slots__ = (
            '_maxsize',
            'getters',
            'putters',
            'hub',
            '_event_unlock',
            'queue',
            '__weakref__',
            'is_shutdown', # 3.13
        )

        def __init__(self, maxsize=None, items=(), _warn_depth=2):
            if maxsize is not None and maxsize <= 0:
                if maxsize == 0:
                    import warnings
                    warnings.warn(
                        'Queue(0) now equivalent to Queue(None); if you want a channel, use Channel',
                        DeprecationWarning,
                        stacklevel=_warn_depth)
                maxsize = None

            self._maxsize = maxsize if maxsize is not None else -1
            # Explicitly maintain order for getters and putters that block
            # so that callers can consistently rely on getting things out
            # in the apparent order they went in. This was once required by
            # imap_unordered. Previously these were set() objects, and the
            # items put in the set have default hash() and eq() methods;
            # under CPython, since new objects tend to have increasing
            # hash values, this tended to roughly maintain order anyway,
            # but that's not true under PyPy. An alternative to a deque
            # (to avoid the linear scan of remove()) might be an
            # OrderedDict, but it's 2.7 only; we don't expect to have so
            # many waiters that removing an arbitrary element is a
            # bottleneck, though.
            self.getters = collections.deque()
            self.putters = collections.deque()
            self.hub = get_hub()
            self._event_unlock = None
            self.queue = self._create_queue(items)
            self.is_shutdown = False

        @property
        def maxsize(self):
            return self._maxsize if self._maxsize > 0 else None

        @maxsize.setter
        def maxsize(self, nv):
            # QQQ make maxsize into a property with setter that schedules unlock if necessary
            if nv is None or nv <= 0:
                self._maxsize = -1
            else:
                self._maxsize = nv

        def copy(self):
            return type(self)(self.maxsize, self.queue)

        def _create_queue(self, items=()):
            return collections.deque(items)

        def _get(self):
            return self.queue.popleft()

        def _peek(self):
            return self.queue[0]

        def _put(self, item):
            self.queue.append(item)

        def __repr__(self):
            return '<%s at %s%s>' % (type(self).__name__, hex(id(self)), self._format())

        def __str__(self):
            return '<%s%s>' % (type(self).__name__, self._format())

        def _format(self):
            result = []
            if self.maxsize is not None:
                result.append('maxsize=%r' % (self.maxsize, ))
            if getattr(self, 'queue', None):
                result.append('queue=%r' % (self.queue, ))
            if self.getters:
                result.append('getters[%s]' % len(self.getters))
            if self.putters:
                result.append('putters[%s]' % len(self.putters))
            if result:
                return ' ' + ' '.join(result)
            return ''

        def qsize(self):
            """Return the size of the queue."""
            return len(self.queue)

        def __len__(self):
            """
            Return the size of the queue. This is the same as :meth:`qsize`.

            .. versionadded: 1.1b3

                Previously, getting len() of a queue would raise a TypeError.
            """

            return self.qsize()

        def __bool__(self):
            """
            A queue object is always True.

            .. versionadded: 1.1b3

               Now that queues support len(), they need to implement ``__bool__``
               to return True for backwards compatibility.
            """
            return True

        def empty(self):
            """Return ``True`` if the queue is empty, ``False`` otherwise."""
            return not self.qsize()

        def full(self):
            """Return ``True`` if the queue is full, ``False`` otherwise.

            ``Queue(None)`` is never full.
            """
            return self._maxsize > 0 and self.qsize() >= self._maxsize

        def put(self, item, block=True, timeout=None):
            """
            Put an item into the queue.

            If optional arg *block* is true and *timeout* is ``None`` (the default),
            block if necessary until a free slot is available. If *timeout* is
            a positive number, it blocks at most *timeout* seconds and raises
            the :class:`Full` exception if no free slot was available within that time.
            Otherwise (*block* is false), put an item on the queue if a free slot
            is immediately available, else raise the :class:`Full` exception (*timeout*
            is ignored in that case).

            ... versionchanged:: 24.10.1
               Now raises a ``ValueError`` for a negative *timeout* in the cases
               that CPython does.
            """
            if self.is_shutdown:
                raise ShutDown
            if self._maxsize == -1 or self.qsize() < self._maxsize:
                # there's a free slot, put an item right away.
                # For compatibility with CPython, verify that the timeout is non-negative.
                if block and timeout is not None and timeout < 0:
                    raise ValueError("'timeout' must be a non-negative number")
                self._put(item)
                if self.getters:
                    self._schedule_unlock()
                return

            if self.hub is getcurrent(): # pylint:disable=undefined-variable
                # We're in the mainloop, so we cannot wait; we can switch to other greenlets though.
                # Check if possible to get a free slot in the queue.
                while self.getters and self.qsize() and self.qsize() >= self._maxsize:
                    getter = self.getters.popleft()
                    getter.switch(getter)
                if self.qsize() < self._maxsize:
                    self._put(item)
                    return
                raise Full

            if block:
                waiter = ItemWaiter(item, self)
                self.putters.append(waiter)
                timeout = Timeout._start_new_or_dummy(timeout, Full)
                try:
                    if self.getters:
                        self._schedule_unlock()
                    result = waiter.get()
                    if result is not waiter:
                        raise InvalidSwitchError("Invalid switch into Queue.put: %r" % (result, ))
                finally:
                    timeout.cancel()
                    _safe_remove(self.putters, waiter)
                return

            raise Full

        def put_nowait(self, item):
            """Put an item into the queue without blocking.

            Only enqueue the item if a free slot is immediately available.
            Otherwise raise the :class:`Full` exception.
            """
            self.put(item, False)

        def __get_or_peek(self, method, block, timeout):
            # Internal helper method. The `method` should be either
            # self._get when called from self.get() or self._peek when
            # called from self.peek(). Call this after the initial check
            # to see if there are items in the queue.

            if self.is_shutdown:
                raise ShutDown

            if block and timeout is not None and timeout < 0:
                raise ValueError("'timeout' must be a non-negative number")
            if self.hub is getcurrent(): # pylint:disable=undefined-variable
                # special case to make get_nowait() or peek_nowait() runnable in the mainloop greenlet
                # there are no items in the queue; try to fix the situation by unlocking putters
                while self.putters:
                    # Note: get() used popleft(), peek used pop(); popleft
                    # is almost certainly correct.
                    self.putters.popleft().put_and_switch()
                    if self.qsize():
                        return method()
                raise Empty

            if not block:
                # We can't block, we're not the hub, and we have nothing
                # to return. No choice but to raise the Empty exception.
                #
                # CAUTION: Calling ``q.get(False)`` in a tight loop won't
                # work like it does in CPython where it should eventually
                # let another thread make progress, because there's never
                # a chance to switch greenlets here. We don't sleep()
                # to enforce that, as that would be a significant behaviour
                # change.
                raise Empty

            waiter = Waiter() # pylint:disable=undefined-variable
            timeout = Timeout._start_new_or_dummy(timeout, Empty)
            try:
                self.getters.append(waiter)
                if self.putters:
                    self._schedule_unlock()
                result = waiter.get()
                if result is not waiter:
                    raise InvalidSwitchError('Invalid switch into Queue.get: %r' % (result, ))
                return method()
            finally:
                timeout.cancel()
                _safe_remove(self.getters, waiter)

        def get(self, block=True, timeout=None):
            """
            Remove and return an item from the queue.

            If optional args *block* is true and *timeout* is ``None`` (the default),
            block if necessary until an item is available. If *timeout* is a positive number,
            it blocks at most *timeout* seconds and raises the :class:`Empty` exception
            if no item was available within that time. Otherwise (*block* is false), return
            an item if one is immediately available, else raise the :class:`Empty` exception
            (*timeout* is ignored in that case).
            """
            if self.qsize():
                if self.putters:
                    self._schedule_unlock()
                return self._get()

            return self.__get_or_peek(self._get, block, timeout)

        def get_nowait(self):
            """Remove and return an item from the queue without blocking.

            Only get an item if one is immediately available. Otherwise
            raise the :class:`Empty` exception.
            """
            return self.get(False)

        def peek(self, block=True, timeout=None):
            """Return an item from the queue without removing it.

            If optional args *block* is true and *timeout* is ``None`` (the default),
            block if necessary until an item is available. If *timeout* is a positive number,
            it blocks at most *timeout* seconds and raises the :class:`Empty` exception
            if no item was available within that time. Otherwise (*block* is false), return
            an item if one is immediately available, else raise the :class:`Empty` exception
            (*timeout* is ignored in that case).
            """
            if self.qsize():
                # This doesn't schedule an unlock like get() does because we're not
                # actually making any space.
                return self._peek()

            return self.__get_or_peek(self._peek, block, timeout)

        def peek_nowait(self):
            """Return an item from the queue without blocking.

            Only return an item if one is immediately available. Otherwise
            raise the :class:`Empty` exception.
            """
            return self.peek(False)

        def _unlock(self):
            while True:
                repeat = False
                if self.putters and (self._maxsize == -1 or self.qsize() < self._maxsize):
                    repeat = True
                    try:
                        putter = self.putters.popleft()
                        self._put(putter.item)
                    except: # pylint:disable=bare-except
                        putter.throw(*sys.exc_info())
                    else:
                        putter.switch(putter)
                if self.getters and self.qsize():
                    repeat = True
                    getter = self.getters.popleft()
                    getter.switch(getter)
                if not repeat:
                    return

        def _schedule_unlock(self):
            if not self._event_unlock:
                self._event_unlock = self.hub.loop.run_callback(self._unlock)

        def __iter__(self):
            return self

        def __next__(self):
            result = self.get()
            if result is StopIteration:
                raise result
            return result

        def shutdown(self, immediate=False):
            """
            "Shut-down the queue, making queue gets and puts raise
            `ShutDown`.

            By default, gets will only raise once the queue is empty. Set
            *immediate* to True to make gets raise immediately instead.

            All blocked callers of `put` and `get` will be unblocked.

            In joinable queues, if *immediate*, a task is marked as done
            for each item remaining in the queue, which may unblock
            callers of `join`.
            """
            self.is_shutdown = True
            if immediate:
                self._drain_for_immediate_shutdown()
            getters = list(self.getters)
            putters = list(self.putters)
            self.getters.clear()
            self.putters.clear()
            for waiter in getters + putters:
                self.hub.loop.run_callback(waiter.throw, ShutDown)

        def _drain_for_immediate_shutdown(self):
            while self.qsize():
                self.get()

    class UnboundQueue(Queue):
        # A specialization of Queue that knows it can never
        # be bound. Changing its maxsize has no effect.

        __slots__ = ()

        def __init__(self, maxsize=None, items=()):
            if maxsize is not None:
                raise ValueError("UnboundQueue has no maxsize")
            Queue.__init__(self, maxsize, items)
            self.putters = None # Will never be used.

        def put(self, item, block=True, timeout=None):
            self._put(item)
            if self.getters:
                self._schedule_unlock()

    class PriorityQueue(Queue):
        '''A subclass of :class:`Queue` that retrieves entries in priority order (lowest first).

        Entries are typically tuples of the form: ``(priority number, data)``.

        .. versionchanged:: 1.2a1
           Any *items* given to the constructor will now be passed through
           :func:`heapq.heapify` to ensure the invariants of this class hold.
           Previously it was just assumed that they were already a heap.
        '''

        __slots__ = ()

        def _create_queue(self, items=()):
            q = list(items)
            _heapify(q)
            return q

        def _put(self, item):
            _heappush(self.queue, item)

        def _get(self):
            return _heappop(self.queue)

    class JoinableQueue(Queue):
        """
        A subclass of :class:`Queue` that additionally has
        :meth:`task_done` and :meth:`join` methods.
        """

        __slots__ = (
            '_cond',
            'unfinished_tasks',
        )

        def __init__(self, maxsize=None, items=(), unfinished_tasks=None):
            """

            .. versionchanged:: 1.1a1
               If *unfinished_tasks* is not given, then all the given *items*
               (if any) will be considered unfinished.

            """
            Queue.__init__(self, maxsize, items, _warn_depth=3)

            from gevent.event import Event
            self._cond = Event()
            self._cond.set()

            if unfinished_tasks:
                self.unfinished_tasks = unfinished_tasks
            elif items:
                self.unfinished_tasks = len(items)
            else:
                self.unfinished_tasks = 0

            if self.unfinished_tasks:
                self._cond.clear()

        def copy(self):
            return type(self)(self.maxsize, self.queue, self.unfinished_tasks)

        def _format(self):
            result = Queue._format(self)
            if self.unfinished_tasks:
                result += ' tasks=%s _cond=%s' % (self.unfinished_tasks, self._cond)
            return result

        def _put(self, item):
            Queue._put(self, item)
            self._did_put_task()

        def _did_put_task(self):
            self.unfinished_tasks += 1
            self._cond.clear()

        def task_done(self):
            '''Indicate that a formerly enqueued task is complete. Used by queue consumer threads.
            For each :meth:`get <Queue.get>` used to fetch a task, a subsequent call to :meth:`task_done` tells the queue
            that the processing on the task is complete.

            If a :meth:`join` is currently blocking, it will resume when all items have been processed
            (meaning that a :meth:`task_done` call was received for every item that had been
            :meth:`put <Queue.put>` into the queue).

            Raises a :exc:`ValueError` if called more times than there were items placed in the queue.
            '''
            if self.unfinished_tasks <= 0:
                raise ValueError('task_done() called too many times')
            self.unfinished_tasks -= 1
            if self.unfinished_tasks == 0:
                self._cond.set()

        def join(self, timeout=None):
            '''
            Block until all items in the queue have been gotten and processed.

            The count of unfinished tasks goes up whenever an item is added to the queue.
            The count goes down whenever a consumer thread calls :meth:`task_done` to indicate
            that the item was retrieved and all work on it is complete. When the count of
            unfinished tasks drops to zero, :meth:`join` unblocks.

            :param float timeout: If not ``None``, then wait no more than this time in seconds
                for all tasks to finish.
            :return: ``True`` if all tasks have finished; if ``timeout`` was given and expired before
                all tasks finished, ``False``.

            .. versionchanged:: 1.1a1
               Add the *timeout* parameter.
            '''
            return self._cond.wait(timeout=timeout)

        def _drain_for_immediate_shutdown(self):
            while self.qsize():
                self.get()
                self.task_done()

    class LifoQueue(JoinableQueue):
        """
        A subclass of :class:`JoinableQueue` that retrieves most recently added entries first.

        .. versionchanged:: 24.10.1
           Now extends :class:`JoinableQueue` instead of just :class:`Queue`.

        """
        __slots__ = ()

        def _create_queue(self, items=()):
            return list(items)

        def _put(self, item):
            self.queue.append(item)
            self._did_put_task()

        def _get(self):
            return self.queue.pop()

        def _peek(self):
            return self.queue[-1]

    class Channel(object):

        __slots__ = (
            'getters',
            'putters',
            'hub',
            '_event_unlock',
            '__weakref__',
        )

        def __init__(self, maxsize=1):
            # We take maxsize to simplify certain kinds of code
            if maxsize != 1:
                raise ValueError("Channels have a maxsize of 1")
            self.getters = collections.deque()
            self.putters = collections.deque()
            self.hub = get_hub()
            self._event_unlock = None

        def __repr__(self):
            return '<%s at %s %s>' % (type(self).__name__, hex(id(self)), self._format())

        def __str__(self):
            return '<%s %s>' % (type(self).__name__, self._format())

        def _format(self):
            result = ''
            if self.getters:
                result += ' getters[%s]' % len(self.getters)
            if self.putters:
                result += ' putters[%s]' % len(self.putters)
            return result

        @property
        def balance(self):
            return len(self.putters) - len(self.getters)

        def qsize(self):
            return 0

        def empty(self):
            return True

        def full(self):
            return True

        def put(self, item, block=True, timeout=None):
            if self.hub is getcurrent(): # pylint:disable=undefined-variable
                if self.getters:
                    getter = self.getters.popleft()
                    getter.switch(item)
                    return
                raise Full

            if not block:
                timeout = 0

            waiter = Waiter() # pylint:disable=undefined-variable
            item = (item, waiter)
            self.putters.append(item)
            timeout = Timeout._start_new_or_dummy(timeout, Full)
            try:
                if self.getters:
                    self._schedule_unlock()
                result = waiter.get()
                if result is not waiter:
                    raise InvalidSwitchError("Invalid switch into Channel.put: %r" % (result, ))
            except:
                _safe_remove(self.putters, item)
                raise
            finally:
                timeout.cancel()

        def put_nowait(self, item):
            self.put(item, False)

        def get(self, block=True, timeout=None):
            if self.hub is getcurrent(): # pylint:disable=undefined-variable
                if self.putters:
                    item, putter = self.putters.popleft()
                    self.hub.loop.run_callback(putter.switch, putter)
                    return item

            if not block:
                timeout = 0

            waiter = Waiter() # pylint:disable=undefined-variable
            timeout = Timeout._start_new_or_dummy(timeout, Empty)
            try:
                self.getters.append(waiter)
                if self.putters:
                    self._schedule_unlock()
                return waiter.get()
            except:
                self.getters.remove(waiter)
                raise
            finally:
                timeout.close()

        def get_nowait(self):
            return self.get(False)

        def _unlock(self):
            while self.putters and self.getters:
                getter = self.getters.popleft()
                item, putter = self.putters.popleft()
                getter.switch(item)
                putter.switch(putter)

        def _schedule_unlock(self):
            if not self._event_unlock:
                self._event_unlock = self.hub.loop.run_callback(self._unlock)

        def __iter__(self):
            return self

        def __next__(self):
            result = self.get()
            if result is StopIteration:
                raise result
            return result

        next = __next__ # Py2

    def _init():
        greenlet_init() # pylint:disable=undefined-variable

    _init()

    from gevent._util import import_c_accel
    import_c_accel(globals(), 'gevent._queue')