Mercurial > cpython-lru_cache-weakref

annotate Lib/Queue.py @ 17581:c1937faabb23 2.1

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Added support for optional explanation parameter to the \versionadded macro. Refactored do_cmd_versionadded() and do_cmd_versionchanged() to do most of the work in a helper function, with the do_cmd_*() wrappers just supplying a portion of the replacement text.
author Fred Drake <fdrake@acm.org>
date Wed, 18 Apr 2001 17:29:14 +0000
parents 79d533934ac1
children c548e726b3bc
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 """A multi-producer, multi-consumer queue."""
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2
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3 class Empty(Exception):
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4 "Exception raised by Queue.get(block=0)/get_nowait()."
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5 pass
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6
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7 class Full(Exception):
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8 "Exception raised by Queue.put(block=0)/put_nowait()."
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9 pass
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10
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11 class Queue:
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12 def __init__(self, maxsize=0):
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13 """Initialize a queue object with a given maximum size.
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14
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15 If maxsize is <= 0, the queue size is infinite.
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16 """
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17 import thread
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18 self._init(maxsize)
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19 self.mutex = thread.allocate_lock()
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20 self.esema = thread.allocate_lock()
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21 self.esema.acquire()
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22 self.fsema = thread.allocate_lock()
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23
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24 def qsize(self):
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25 """Return the approximate size of the queue (not reliable!)."""
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26 self.mutex.acquire()
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27 n = self._qsize()
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28 self.mutex.release()
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29 return n
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30
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31 def empty(self):
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32 """Return 1 if the queue is empty, 0 otherwise (not reliable!)."""
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33 self.mutex.acquire()
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34 n = self._empty()
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35 self.mutex.release()
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36 return n
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37
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38 def full(self):
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39 """Return 1 if the queue is full, 0 otherwise (not reliable!)."""
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40 self.mutex.acquire()
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41 n = self._full()
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42 self.mutex.release()
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43 return n
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44
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45 def put(self, item, block=1):
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46 """Put an item into the queue.
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47
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48 If optional arg 'block' is 1 (the default), block if
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49 necessary until a free slot is available. Otherwise (block
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50 is 0), put an item on the queue if a free slot is immediately
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51 available, else raise the Full exception.
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52 """
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53 if block:
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54 self.fsema.acquire()
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55 elif not self.fsema.acquire(0):
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56 raise Full
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57 self.mutex.acquire()
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58 was_empty = self._empty()
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59 self._put(item)
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60 if was_empty:
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61 self.esema.release()
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62 if not self._full():
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63 self.fsema.release()
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64 self.mutex.release()
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65
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66 def put_nowait(self, item):
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67 """Put an item into the queue without blocking.
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68
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69 Only enqueue the item if a free slot is immediately available.
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70 Otherwise raise the Full exception.
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71 """
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72 return self.put(item, 0)
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73
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74 def get(self, block=1):
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75 """Remove and return an item from the queue.
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76
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77 If optional arg 'block' is 1 (the default), block if
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78 necessary until an item is available. Otherwise (block is 0),
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79 return an item if one is immediately available, else raise the
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80 Empty exception.
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81 """
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82 if block:
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83 self.esema.acquire()
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84 elif not self.esema.acquire(0):
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85 raise Empty
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86 self.mutex.acquire()
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87 was_full = self._full()
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88 item = self._get()
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89 if was_full:
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90 self.fsema.release()
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91 if not self._empty():
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92 self.esema.release()
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93 self.mutex.release()
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94 return item
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95
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96 def get_nowait(self):
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97 """Remove and return an item from the queue without blocking.
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98
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99 Only get an item if one is immediately available. Otherwise
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100 raise the Empty exception.
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101 """
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102 return self.get(0)
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103
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104 # Override these methods to implement other queue organizations
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105 # (e.g. stack or priority queue).
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106 # These will only be called with appropriate locks held
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107
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108 # Initialize the queue representation
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109 def _init(self, maxsize):
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110 self.maxsize = maxsize
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111 self.queue = []
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112
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113 def _qsize(self):
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114 return len(self.queue)
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115
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116 # Check whether the queue is empty
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117 def _empty(self):
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118 return not self.queue
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119
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120 # Check whether the queue is full
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121 def _full(self):
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122 return self.maxsize > 0 and len(self.queue) == self.maxsize
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123
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124 # Put a new item in the queue
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125 def _put(self, item):
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126 self.queue.append(item)
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127
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128 # Get an item from the queue
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129 def _get(self):
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130 item = self.queue[0]
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131 del self.queue[0]
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132 return item