(Queue.Empty): When class based exceptions are in force, derive this

class from the standard base exception Exception.  Otherwise define
Queue.Empty as a string exception.

(Queue): 8-space to 4-space indentation conversion.  Also, basically
recast all method comments into docstrings.
This commit is contained in:
Barry Warsaw 1997-11-20 19:56:38 +00:00
parent 17c8e781c0
commit 3d96d522ec
1 changed files with 119 additions and 105 deletions

View File

@ -1,12 +1,20 @@
# A multi-producer, multi-consumer queue. # A multi-producer, multi-consumer queue.
Empty = 'Queue.Empty' # Exception raised by get_nowait() # define this exception to be compatible with Python 1.5's class
# exceptions, but also when -X option is used.
try:
class Empty(Exception):
pass
except TypeError:
# string based exceptions
Empty = 'Queue.Empty' # Exception raised by get_nowait()
class Queue: class Queue:
# Initialize a queue object with a given maximum size
# (If maxsize is <= 0, the maximum size is infinite)
def __init__(self, maxsize): def __init__(self, maxsize):
"""Initialize a queue object with a given maximum size.
If maxsize is <= 0, the queue size is infinite.
"""
import thread import thread
self._init(maxsize) self._init(maxsize)
self.mutex = thread.allocate_lock() self.mutex = thread.allocate_lock()
@ -14,29 +22,29 @@ class Queue:
self.esema.acquire_lock() self.esema.acquire_lock()
self.fsema = thread.allocate_lock() self.fsema = thread.allocate_lock()
# Get an approximation of the queue size (not reliable!)
def qsize(self): def qsize(self):
"""Returns the approximate size of the queue (not reliable!)."""
self.mutex.acquire_lock() self.mutex.acquire_lock()
n = self._qsize() n = self._qsize()
self.mutex.release_lock() self.mutex.release_lock()
return n return n
# Check if the queue is empty (not reliable!)
def empty(self): def empty(self):
"""Returns 1 if the queue is empty, 0 otherwise (not reliable!)."""
self.mutex.acquire_lock() self.mutex.acquire_lock()
n = self._empty() n = self._empty()
self.mutex.release_lock() self.mutex.release_lock()
return n return n
# Check if the queue is full (not reliable!)
def full(self): def full(self):
"""Returns 1 if the queue is full, 0 otherwise (not reliable!)."""
self.mutex.acquire_lock() self.mutex.acquire_lock()
n = self._full() n = self._full()
self.mutex.release_lock() self.mutex.release_lock()
return n return n
# Put a new item into the queue
def put(self, item): def put(self, item):
"""Put an item into the queue."""
self.fsema.acquire_lock() self.fsema.acquire_lock()
self.mutex.acquire_lock() self.mutex.acquire_lock()
was_empty = self._empty() was_empty = self._empty()
@ -47,9 +55,10 @@ class Queue:
self.fsema.release_lock() self.fsema.release_lock()
self.mutex.release_lock() self.mutex.release_lock()
# Get an item from the queue,
# blocking if necessary until one is available
def get(self): def get(self):
"""Gets and returns an item from the queue.
This method blocks if necessary until an item is available.
"""
self.esema.acquire_lock() self.esema.acquire_lock()
self.mutex.acquire_lock() self.mutex.acquire_lock()
was_full = self._full() was_full = self._full()
@ -64,10 +73,15 @@ class Queue:
# Get an item from the queue if one is immediately available, # Get an item from the queue if one is immediately available,
# raise Empty if the queue is empty or temporarily unavailable # raise Empty if the queue is empty or temporarily unavailable
def get_nowait(self): def get_nowait(self):
"""Gets and returns 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.
"""
locked = self.esema.acquire_lock(0) locked = self.esema.acquire_lock(0)
self.mutex.acquire_lock() self.mutex.acquire_lock()
if self._empty(): if self._empty():
# The queue is empyt -- we can't have esema # The queue is empty -- we can't have esema
self.mutex.release_lock() self.mutex.release_lock()
raise Empty raise Empty
if not locked: if not locked: