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(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.
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Lines changed: 130 additions & 116 deletions

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‎Lib/Queue.py‎

Lines changed: 130 additions & 116 deletions
Original file line numberDiff line numberDiff line change
@@ -1,121 +1,135 @@
11
# A multi-producer, multi-consumer queue.
22

3-
Empty = 'Queue.Empty' # Exception raised by get_nowait()
3+
# define this exception to be compatible with Python 1.5's class
4+
# exceptions, but also when -X option is used.
5+
try:
6+
class Empty(Exception):
7+
pass
8+
except TypeError:
9+
# string based exceptions
10+
Empty = 'Queue.Empty' # Exception raised by get_nowait()
411

512
class Queue:
6-
7-
# Initialize a queue object with a given maximum size
8-
# (If maxsize is <= 0, the maximum size is infinite)
9-
def __init__(self, maxsize):
10-
import thread
11-
self._init(maxsize)
12-
self.mutex = thread.allocate_lock()
13-
self.esema = thread.allocate_lock()
14-
self.esema.acquire_lock()
15-
self.fsema = thread.allocate_lock()
16-
17-
# Get an approximation of the queue size (not reliable!)
18-
def qsize(self):
19-
self.mutex.acquire_lock()
20-
n = self._qsize()
21-
self.mutex.release_lock()
22-
return n
23-
24-
# Check if the queue is empty (not reliable!)
25-
def empty(self):
26-
self.mutex.acquire_lock()
27-
n = self._empty()
28-
self.mutex.release_lock()
29-
return n
30-
31-
# Check if the queue is full (not reliable!)
32-
def full(self):
33-
self.mutex.acquire_lock()
34-
n = self._full()
35-
self.mutex.release_lock()
36-
return n
37-
38-
# Put a new item into the queue
39-
def put(self, item):
40-
self.fsema.acquire_lock()
41-
self.mutex.acquire_lock()
42-
was_empty = self._empty()
43-
self._put(item)
44-
if was_empty:
45-
self.esema.release_lock()
46-
if not self._full():
47-
self.fsema.release_lock()
48-
self.mutex.release_lock()
49-
50-
# Get an item from the queue,
51-
# blocking if necessary until one is available
52-
def get(self):
53-
self.esema.acquire_lock()
54-
self.mutex.acquire_lock()
55-
was_full = self._full()
56-
item = self._get()
57-
if was_full:
58-
self.fsema.release_lock()
59-
if not self._empty():
60-
self.esema.release_lock()
61-
self.mutex.release_lock()
62-
return item
63-
64-
# Get an item from the queue if one is immediately available,
65-
# raise Empty if the queue is empty or temporarily unavailable
66-
def get_nowait(self):
67-
locked = self.esema.acquire_lock(0)
68-
self.mutex.acquire_lock()
69-
if self._empty():
70-
# The queue is empyt -- we can't have esema
71-
self.mutex.release_lock()
72-
raise Empty
73-
if not locked:
74-
locked = self.esema.acquire_lock(0)
75-
if not locked:
76-
# Somebody else has esema
77-
# but we have mutex --
78-
# go out of their way
79-
self.mutex.release_lock()
80-
raise Empty
81-
was_full = self._full()
82-
item = self._get()
83-
if was_full:
84-
self.fsema.release_lock()
85-
if not self._empty():
86-
self.esema.release_lock()
13+
def __init__(self, maxsize):
14+
"""Initialize a queue object with a given maximum size.
15+
16+
If maxsize is <= 0, the queue size is infinite.
17+
"""
18+
import thread
19+
self._init(maxsize)
20+
self.mutex = thread.allocate_lock()
21+
self.esema = thread.allocate_lock()
22+
self.esema.acquire_lock()
23+
self.fsema = thread.allocate_lock()
24+
25+
def qsize(self):
26+
"""Returns the approximate size of the queue (not reliable!)."""
27+
self.mutex.acquire_lock()
28+
n = self._qsize()
29+
self.mutex.release_lock()
30+
return n
31+
32+
def empty(self):
33+
"""Returns 1 if the queue is empty, 0 otherwise (not reliable!)."""
34+
self.mutex.acquire_lock()
35+
n = self._empty()
36+
self.mutex.release_lock()
37+
return n
38+
39+
def full(self):
40+
"""Returns 1 if the queue is full, 0 otherwise (not reliable!)."""
41+
self.mutex.acquire_lock()
42+
n = self._full()
43+
self.mutex.release_lock()
44+
return n
45+
46+
def put(self, item):
47+
"""Put an item into the queue."""
48+
self.fsema.acquire_lock()
49+
self.mutex.acquire_lock()
50+
was_empty = self._empty()
51+
self._put(item)
52+
if was_empty:
53+
self.esema.release_lock()
54+
if not self._full():
55+
self.fsema.release_lock()
56+
self.mutex.release_lock()
57+
58+
def get(self):
59+
"""Gets and returns an item from the queue.
60+
This method blocks if necessary until an item is available.
61+
"""
62+
self.esema.acquire_lock()
63+
self.mutex.acquire_lock()
64+
was_full = self._full()
65+
item = self._get()
66+
if was_full:
67+
self.fsema.release_lock()
68+
if not self._empty():
69+
self.esema.release_lock()
70+
self.mutex.release_lock()
71+
return item
72+
73+
# Get an item from the queue if one is immediately available,
74+
# raise Empty if the queue is empty or temporarily unavailable
75+
def get_nowait(self):
76+
"""Gets and returns an item from the queue.
77+
Only gets an item if one is immediately available, Otherwise
78+
this raises the Empty exception if the queue is empty or
79+
temporarily unavailable.
80+
"""
81+
locked = self.esema.acquire_lock(0)
82+
self.mutex.acquire_lock()
83+
if self._empty():
84+
# The queue is empty -- we can't have esema
85+
self.mutex.release_lock()
86+
raise Empty
87+
if not locked:
88+
locked = self.esema.acquire_lock(0)
89+
if not locked:
90+
# Somebody else has esema
91+
# but we have mutex --
92+
# go out of their way
8793
self.mutex.release_lock()
88-
return item
89-
90-
# XXX Need to define put_nowait() as well.
91-
92-
93-
# Override these methods to implement other queue organizations
94-
# (e.g. stack or priority queue).
95-
# These will only be called with appropriate locks held
96-
97-
# Initialize the queue representation
98-
def _init(self, maxsize):
99-
self.maxsize = maxsize
100-
self.queue = []
101-
102-
def _qsize(self):
103-
return len(self.queue)
104-
105-
# Check wheter the queue is empty
106-
def _empty(self):
107-
return not self.queue
108-
109-
# Check whether the queue is full
110-
def _full(self):
111-
return self.maxsize > 0 and len(self.queue) == self.maxsize
112-
113-
# Put a new item in the queue
114-
def _put(self, item):
115-
self.queue.append(item)
116-
117-
# Get an item from the queue
118-
def _get(self):
119-
item = self.queue[0]
120-
del self.queue[0]
121-
return item
94+
raise Empty
95+
was_full = self._full()
96+
item = self._get()
97+
if was_full:
98+
self.fsema.release_lock()
99+
if not self._empty():
100+
self.esema.release_lock()
101+
self.mutex.release_lock()
102+
return item
103+
104+
# XXX Need to define put_nowait() as well.
105+
106+
107+
# Override these methods to implement other queue organizations
108+
# (e.g. stack or priority queue).
109+
# These will only be called with appropriate locks held
110+
111+
# Initialize the queue representation
112+
def _init(self, maxsize):
113+
self.maxsize = maxsize
114+
self.queue = []
115+
116+
def _qsize(self):
117+
return len(self.queue)
118+
119+
# Check wheter the queue is empty
120+
def _empty(self):
121+
return not self.queue
122+
123+
# Check whether the queue is full
124+
def _full(self):
125+
return self.maxsize > 0 and len(self.queue) == self.maxsize
126+
127+
# Put a new item in the queue
128+
def _put(self, item):
129+
self.queue.append(item)
130+
131+
# Get an item from the queue
132+
def _get(self):
133+
item = self.queue[0]
134+
del self.queue[0]
135+
return item

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