class Result(object):
"""
Result is an internal object which is meant to be used like a Future, but being more
lightweight and supporting a single waiter. Example:
result = Result()
def f1():
with result:
some_async_func()
return result.get()
def some_async_func():
# this function runs in a different task
...
result.set_value(42)
"""
__slots__ = ['_lock', '_cond', '_locked', '_used', '_exc', '_value']
def __init__(self):
self._lock = Lock()
self._cond = Condition(Lock())
self._locked = False
self._used = False
self._exc = self._value = Null
def acquire(self):
self._lock.acquire()
self._locked = True
def release(self):
self._lock.release()
self._locked = False
self._used = False
self._exc = self._value = Null
def get(self):
assert self._locked
assert not self._used
try:
with self._cond:
if self._exc == self._value == Null:
self._cond.wait()
if self._exc != Null:
raise self._exc
assert self._value != Null
return self._value
finally:
self._used = True
self._exc = self._value = Null
def set_value(self, value):
assert self._locked
assert not self._used
assert self._exc == self._value == Null
with self._cond:
self._value = value
self._cond.notify_all()
def set_exception(self, value):
assert self._locked
assert not self._used
assert self._exc == self._value == Null
with self._cond:
self._exc = value
self._cond.notify_all()
def __enter__(self):
self.acquire()
def __exit__(self, typ, val, tb):
self.release()
class Queue(object):
"""Create a queue object with a given maximum size.
If maxsize is <= 0, the queue size is infinite.
"""
def __init__(self, maxsize=0):
self.maxsize = maxsize
self._init(maxsize)
# mutex must be held whenever the queue is mutating. All methods
# that acquire mutex must release it before returning. mutex
# is shared between the three conditions, so acquiring and
# releasing the conditions also acquires and releases mutex.
self.mutex = Lock()
# Notify not_empty whenever an item is added to the queue; a
# task waiting to get is notified then.
self.not_empty = Condition(self.mutex)
# Notify not_full whenever an item is removed from the queue;
# a task waiting to put is notified then.
self.not_full = Condition(self.mutex)
# Notify all_tasks_done whenever the number of unfinished tasks
# drops to zero; task waiting to join() is notified to resume
self.all_tasks_done = Condition(self.mutex)
self.unfinished_tasks = 0
def task_done(self):
"""Indicate that a formerly enqueued task is complete.
Used by Queue consumer tasks. For each get() used to fetch a task,
a subsequent call to task_done() tells the queue that the processing
on the task is complete.
If a join() is currently blocking, it will resume when all items
have been processed (meaning that a task_done() call was received
for every item that had been put() into the queue).
Raises a ValueError if called more times than there were items
placed in the queue.
"""
self.all_tasks_done.acquire()
try:
unfinished = self.unfinished_tasks - 1
if unfinished <= 0:
if unfinished < 0:
raise ValueError('task_done() called too many times')
self.all_tasks_done.notify_all()
self.unfinished_tasks = unfinished
finally:
self.all_tasks_done.release()
def join(self):
"""Blocks 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 task calls task_done()
to indicate the item was retrieved and all work on it is complete.
When the count of unfinished tasks drops to zero, join() unblocks.
"""
self.all_tasks_done.acquire()
try:
while self.unfinished_tasks:
self.all_tasks_done.wait()
finally:
self.all_tasks_done.release()
def qsize(self):
"""Return the approximate size of the queue (not reliable!)."""
self.mutex.acquire()
n = self._qsize()
self.mutex.release()
return n
def empty(self):
"""Return True if the queue is empty, False otherwise (not reliable!).
This method is likely to be removed at some point. Use qsize() == 0
as a direct substitute, but be aware that either approach risks a race
condition where a queue can grow before the result of empty() or
qsize() can be used.
To create code that needs to wait for all queued tasks to be
completed, the preferred technique is to use the join() method.
"""
self.mutex.acquire()
n = not self._qsize()
self.mutex.release()
return n
def full(self):
"""Return True if the queue is full, False otherwise (not reliable!).
This method is likely to be removed at some point. Use qsize() >= n
as a direct substitute, but be aware that either approach risks a race
condition where a queue can shrink before the result of full() or
qsize() can be used.
"""
self.mutex.acquire()
n = 0 < self.maxsize <= self._qsize()
self.mutex.release()
return n
def put(self, item, block=True, timeout=None):
"""Put an item into the queue.
If optional args '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 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 Full exception ('timeout'
is ignored in that case).
"""
self.not_full.acquire()
try:
if self.maxsize > 0:
if not block:
if self._qsize() >= self.maxsize:
raise Full
elif timeout is None:
while self._qsize() >= self.maxsize:
self.not_full.wait()
elif timeout < 0:
raise ValueError("'timeout' must be a positive number")
else:
endtime = _time() + timeout
while self._qsize() >= self.maxsize:
remaining = endtime - _time()
if remaining <= 0.0:
raise Full
self.not_full.wait(remaining)
self._put(item)
self.unfinished_tasks += 1
self.not_empty.notify()
finally:
self.not_full.release()
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 Full exception.
"""
return self.put(item, False)
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 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 Empty exception ('timeout' is ignored
in that case).
"""
self.not_empty.acquire()
try:
if not block:
if not self._qsize():
raise Empty
elif timeout is None:
while not self._qsize():
self.not_empty.wait()
elif timeout < 0:
raise ValueError("'timeout' must be a positive number")
else:
endtime = _time() + timeout
while not self._qsize():
remaining = endtime - _time()
if remaining <= 0.0:
raise Empty
self.not_empty.wait(remaining)
item = self._get()
self.not_full.notify()
return item
finally:
self.not_empty.release()
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 Empty exception.
"""
return self.get(False)
# Override these methods to implement other queue organizations
# (e.g. stack or priority queue).
# These will only be called with appropriate locks held
# Initialize the queue representation
def _init(self, maxsize):
self.queue = deque()
def _qsize(self):
return len(self.queue)
# Put a new item in the queue
def _put(self, item):
self.queue.append(item)
# Get an item from the queue
def _get(self):
return self.queue.popleft()
class Queue(object):
"""Create a queue object with a given maximum size.
If maxsize is <= 0, the queue size is infinite.
"""
def __init__(self, maxsize=0):
self.maxsize = maxsize
self._init(maxsize)
# mutex must be held whenever the queue is mutating. All methods
# that acquire mutex must release it before returning. mutex
# is shared between the three conditions, so acquiring and
# releasing the conditions also acquires and releases mutex.
self.mutex = Lock()
# Notify not_empty whenever an item is added to the queue; a
# task waiting to get is notified then.
self.not_empty = Condition(self.mutex)
# Notify not_full whenever an item is removed from the queue;
# a task waiting to put is notified then.
self.not_full = Condition(self.mutex)
# Notify all_tasks_done whenever the number of unfinished tasks
# drops to zero; task waiting to join() is notified to resume
self.all_tasks_done = Condition(self.mutex)
self.unfinished_tasks = 0
def task_done(self):
"""Indicate that a formerly enqueued task is complete.
Used by Queue consumer tasks. For each get() used to fetch a task,
a subsequent call to task_done() tells the queue that the processing
on the task is complete.
If a join() is currently blocking, it will resume when all items
have been processed (meaning that a task_done() call was received
for every item that had been put() into the queue).
Raises a ValueError if called more times than there were items
placed in the queue.
"""
self.all_tasks_done.acquire()
try:
unfinished = self.unfinished_tasks - 1
if unfinished <= 0:
if unfinished < 0:
raise ValueError('task_done() called too many times')
self.all_tasks_done.notify_all()
self.unfinished_tasks = unfinished
finally:
self.all_tasks_done.release()
def join(self):
"""Blocks 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 task calls task_done()
to indicate the item was retrieved and all work on it is complete.
When the count of unfinished tasks drops to zero, join() unblocks.
"""
self.all_tasks_done.acquire()
try:
while self.unfinished_tasks:
self.all_tasks_done.wait()
finally:
self.all_tasks_done.release()
def qsize(self):
"""Return the approximate size of the queue (not reliable!)."""
self.mutex.acquire()
n = self._qsize()
self.mutex.release()
return n
def empty(self):
"""Return True if the queue is empty, False otherwise (not reliable!).
This method is likely to be removed at some point. Use qsize() == 0
as a direct substitute, but be aware that either approach risks a race
condition where a queue can grow before the result of empty() or
qsize() can be used.
To create code that needs to wait for all queued tasks to be
completed, the preferred technique is to use the join() method.
"""
self.mutex.acquire()
n = not self._qsize()
self.mutex.release()
return n
def full(self):
"""Return True if the queue is full, False otherwise (not reliable!).
This method is likely to be removed at some point. Use qsize() >= n
as a direct substitute, but be aware that either approach risks a race
condition where a queue can shrink before the result of full() or
qsize() can be used.
"""
self.mutex.acquire()
n = 0 < self.maxsize <= self._qsize()
self.mutex.release()
return n
def put(self, item, block=True, timeout=None):
"""Put an item into the queue.
If optional args '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 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 Full exception ('timeout'
is ignored in that case).
"""
self.not_full.acquire()
try:
if self.maxsize > 0:
if not block:
if self._qsize() >= self.maxsize:
raise Full
elif timeout is None:
while self._qsize() >= self.maxsize:
self.not_full.wait()
elif timeout < 0:
raise ValueError("'timeout' must be a positive number")
else:
if self._qsize() >= self.maxsize:
self.not_full.wait(timeout)
if self._qsize() >= self.maxsize:
raise Full
self._put(item)
self.unfinished_tasks += 1
self.not_empty.notify()
finally:
self.not_full.release()
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 Full exception.
"""
return self.put(item, False)
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 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 Empty exception ('timeout' is ignored
in that case).
"""
self.not_empty.acquire()
try:
if not block:
if not self._qsize():
raise Empty
elif timeout is None:
while not self._qsize():
self.not_empty.wait()
elif timeout < 0:
raise ValueError("'timeout' must be a positive number")
else:
if not self._qsize():
self.not_empty.wait(timeout)
if not self._qsize():
raise Empty
item = self._get()
self.not_full.notify()
return item
finally:
self.not_empty.release()
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 Empty exception.
"""
return self.get(False)
# Override these methods to implement other queue organizations
# (e.g. stack or priority queue).
# These will only be called with appropriate locks held
# Initialize the queue representation
def _init(self, maxsize):
self.queue = deque()
def _qsize(self):
return len(self.queue)
# Put a new item in the queue
def _put(self, item):
self.queue.append(item)
# Get an item from the queue
def _get(self):
return self.queue.popleft()
class Result(object):
"""
Result is an internal object which is meant to be used like a Future, but being more
lightweight and supporting a single waiter. Example:
result = Result()
def f1():
with result:
some_async_func()
return result.get()
def some_async_func():
# this function runs in a different task
...
result.set_value(42)
"""
__slots__ = ['_lock', '_cond', '_locked', '_used', '_exc', '_value']
def __init__(self):
self._lock = Lock()
self._cond = Condition(Lock())
self._locked = False
self._used = False
self._exc = self._value = Null
def acquire(self):
self._lock.acquire()
self._locked = True
def release(self):
self._lock.release()
self._locked = False
self._used = False
self._exc = self._value = Null
def get(self):
assert self._locked
assert not self._used
try:
with self._cond:
if self._exc == self._value == Null:
self._cond.wait()
if self._exc != Null:
raise self._exc
assert self._value != Null
return self._value
finally:
self._used = True
self._exc = self._value = Null
def set_value(self, value):
assert self._locked
assert not self._used
assert self._exc == self._value == Null
with self._cond:
self._value = value
self._cond.notify_all()
def set_exception(self, value):
assert self._locked
assert not self._used
assert self._exc == self._value == Null
with self._cond:
self._exc = value
self._cond.notify_all()
def __enter__(self):
self.acquire()
def __exit__(self, typ, val, tb):
self.release()