diff options
| -rw-r--r-- | Lib/Queue.py | 82 |
1 files changed, 40 insertions, 42 deletions
diff --git a/Lib/Queue.py b/Lib/Queue.py index 5e698ea..79c4880 100644 --- a/Lib/Queue.py +++ b/Lib/Queue.py @@ -5,9 +5,14 @@ try: class Empty(Exception): pass + class Full(Exception): + pass except TypeError: # string based exceptions - Empty = 'Queue.Empty' # Exception raised by get_nowait() + # exception raised by get(block=0)/get_nowait() + Empty = 'Queue.Empty' + # exception raised by put(block=0)/put_nowait() + Full = 'Queue.Full' class Queue: def __init__(self, maxsize): @@ -23,32 +28,38 @@ class Queue: self.fsema = thread.allocate_lock() def qsize(self): - """Returns the approximate size of the queue (not reliable!).""" + """Return the approximate size of the queue (not reliable!).""" self.mutex.acquire() n = self._qsize() self.mutex.release() return n def empty(self): - """Returns 1 if the queue is empty, 0 otherwise (not reliable!).""" + """Return 1 if the queue is empty, 0 otherwise (not reliable!).""" self.mutex.acquire() n = self._empty() self.mutex.release() return n def full(self): - """Returns 1 if the queue is full, 0 otherwise (not reliable!).""" + """Return 1 if the queue is full, 0 otherwise (not reliable!).""" self.mutex.acquire() n = self._full() self.mutex.release() return n - def put(self, item): + def put(self, item, block=1): """Put an item into the queue. - If the queue is full, block until a free slot is avaiable. - """ - self.fsema.acquire() + If optional arg 'block' is 1 (the default), block if + necessary until a free slot is available. Otherwise (block + is 0), put an item on the queue if a free slot is immediately + available, else raise the Full exception. + """ + if block: + self.fsema.acquire() + elif not self.fsema.acquire(0): + raise Full self.mutex.acquire() was_empty = self._empty() self._put(item) @@ -58,45 +69,27 @@ class Queue: self.fsema.release() self.mutex.release() - def get(self): - """Gets and returns an item from the queue. + def put_nowait(self, item): + """Put an item into the queue without blocking. - This method blocks if necessary until an item is available. + Only enqueue the item if a free slot is immediately available. + Otherwise raise the Full exception. """ - self.esema.acquire() - self.mutex.acquire() - was_full = self._full() - item = self._get() - if was_full: - self.fsema.release() - if not self._empty(): - self.esema.release() - self.mutex.release() - return item + return self.put(item, 0) - # Get an item from the queue if one is immediately available, - # raise Empty if the queue is empty or temporarily unavailable - def get_nowait(self): - """Gets and returns an item from the queue. + def get(self, block=1): + """Remove and return an item from the queue. - Only gets an item if one is immediately available, Otherwise - this raises the Empty exception if the queue is empty or - temporarily unavailable. + If optional arg 'block' is 1 (the default), block if + necessary until an item is available. Otherwise (block is 0), + return an item if one is immediately available, else raise the + Empty exception. """ - locked = self.esema.acquire(0) - self.mutex.acquire() - if self._empty(): - # The queue is empty -- we can't have esema - self.mutex.release() + if block: + self.esema.acquire() + elif not self.esema.acquire(0): raise Empty - if not locked: - locked = self.esema.acquire(0) - if not locked: - # Somebody else has esema - # but we have mutex -- - # go out of their way - self.mutex.release() - raise Empty + self.mutex.acquire() was_full = self._full() item = self._get() if was_full: @@ -106,8 +99,13 @@ class Queue: self.mutex.release() return item - # XXX Need to define put_nowait() as well. + 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(0) # Override these methods to implement other queue organizations # (e.g. stack or priority queue). |