"""A multi-producer, multi-consumer queue."""
from time
import time
as _time
from collections
import deque
__all__
= ['Empty', 'Full', 'Queue']
"Exception raised by Queue.get(block=0)/get_nowait()."
"Exception raised by Queue.put(block=0)/put_nowait()."
def __init__(self
, maxsize
=0):
"""Initialize a queue object with a given maximum size.
If maxsize is <= 0, the queue size is infinite.
import dummy_threading
as threading
# mutex must be held whenever the queue is mutating. All methods
# that acquire mutex must release it before returning. mutex
# is shared between the two conditions, so acquiring and
# releasing the conditions also acquires and releases mutex.
self
.mutex
= threading
.Lock()
# Notify not_empty whenever an item is added to the queue; a
# thread waiting to get is notified then.
self
.not_empty
= threading
.Condition(self
.mutex
)
# Notify not_full whenever an item is removed from the queue;
# a thread waiting to put is notified then.
self
.not_full
= threading
.Condition(self
.mutex
)
"""Return the approximate size of the queue (not reliable!)."""
"""Return True if the queue is empty, False otherwise (not reliable!)."""
"""Return True if the queue is full, False otherwise (not reliable!)."""
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).
raise ValueError("'timeout' must be a positive number")
endtime
= _time() + timeout
remaining
= endtime
- _time()
self
.not_full
.wait(remaining
)
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
raise ValueError("'timeout' must be a positive number")
endtime
= _time() + timeout
remaining
= endtime
- _time()
self
.not_empty
.wait(remaining
)
"""Remove and return an item from the queue without blocking.
Only get an item if one is immediately available. Otherwise
raise the Empty exception.
# 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
):
# Check whether the queue is empty
# Check whether the queue is full
return self
.maxsize
> 0 and len(self
.queue
) == self
.maxsize
# Put a new item in the queue
# Get an item from the queue
return self
.queue
.popleft()