Mercurial > cpython-lru_cache-weakref

annotate Lib/Queue.py @ 13163:a09e8635534d legacy-trunk

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Don't try to guess the name of a .def file -- if one is supplied, use it, otherwise just generate an '/export:' option.
author Greg Ward <gward@python.net>
date Thu, 29 Jun 2000 23:09:20 +0000
parents a195962e389c
children eef321b6e41c
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rev   line source
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e34991022571 Mass patch by Ka-Ping Yee:
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1 """A multi-producer, multi-consumer queue."""
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2
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3 # define this exception to be compatible with Python 1.5's class
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4 # exceptions, but also when -X option is used.
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5 try:
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6 class Empty(Exception):
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7 pass
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8 class Full(Exception):
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9 pass
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10 except TypeError:
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11 # string based exceptions
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12 # exception raised by get(block=0)/get_nowait()
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13 Empty = 'Queue.Empty'
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14 # exception raised by put(block=0)/put_nowait()
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15 Full = 'Queue.Full'
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16
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17 class Queue:
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18 def __init__(self, maxsize=0):
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19 """Initialize a queue object with a given maximum size.
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20
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21 If maxsize is <= 0, the queue size is infinite.
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22 """
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23 import thread
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24 self._init(maxsize)
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25 self.mutex = thread.allocate_lock()
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26 self.esema = thread.allocate_lock()
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27 self.esema.acquire()
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28 self.fsema = thread.allocate_lock()
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29
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30 def qsize(self):
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31 """Return the approximate size of the queue (not reliable!)."""
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32 self.mutex.acquire()
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33 n = self._qsize()
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34 self.mutex.release()
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35 return n
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36
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37 def empty(self):
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38 """Return 1 if the queue is empty, 0 otherwise (not reliable!)."""
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39 self.mutex.acquire()
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40 n = self._empty()
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41 self.mutex.release()
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42 return n
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43
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44 def full(self):
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45 """Return 1 if the queue is full, 0 otherwise (not reliable!)."""
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46 self.mutex.acquire()
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47 n = self._full()
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48 self.mutex.release()
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49 return n
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50
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51 def put(self, item, block=1):
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52 """Put an item into the queue.
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53
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54 If optional arg 'block' is 1 (the default), block if
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55 necessary until a free slot is available. Otherwise (block
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56 is 0), put an item on the queue if a free slot is immediately
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57 available, else raise the Full exception.
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58 """
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59 if block:
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60 self.fsema.acquire()
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61 elif not self.fsema.acquire(0):
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62 raise Full
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63 self.mutex.acquire()
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64 was_empty = self._empty()
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65 self._put(item)
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66 if was_empty:
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67 self.esema.release()
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68 if not self._full():
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69 self.fsema.release()
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70 self.mutex.release()
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71
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72 def put_nowait(self, item):
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73 """Put an item into the queue without blocking.
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74
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75 Only enqueue the item if a free slot is immediately available.
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76 Otherwise raise the Full exception.
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77 """
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78 return self.put(item, 0)
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79
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80 def get(self, block=1):
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81 """Remove and return an item from the queue.
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82
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83 If optional arg 'block' is 1 (the default), block if
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84 necessary until an item is available. Otherwise (block is 0),
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85 return an item if one is immediately available, else raise the
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86 Empty exception.
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87 """
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88 if block:
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89 self.esema.acquire()
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90 elif not self.esema.acquire(0):
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91 raise Empty
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92 self.mutex.acquire()
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93 was_full = self._full()
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94 item = self._get()
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95 if was_full:
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96 self.fsema.release()
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97 if not self._empty():
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98 self.esema.release()
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99 self.mutex.release()
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100 return item
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101
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102 def get_nowait(self):
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103 """Remove and return an item from the queue without blocking.
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104
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105 Only get an item if one is immediately available. Otherwise
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106 raise the Empty exception.
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107 """
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108 return self.get(0)
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109
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110 # Override these methods to implement other queue organizations
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111 # (e.g. stack or priority queue).
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112 # These will only be called with appropriate locks held
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113
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114 # Initialize the queue representation
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115 def _init(self, maxsize):
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116 self.maxsize = maxsize
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117 self.queue = []
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118
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119 def _qsize(self):
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120 return len(self.queue)
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121
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122 # Check whether the queue is empty
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123 def _empty(self):
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124 return not self.queue
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125
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126 # Check whether the queue is full
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127 def _full(self):
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128 return self.maxsize > 0 and len(self.queue) == self.maxsize
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129
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130 # Put a new item in the queue
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131 def _put(self, item):
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132 self.queue.append(item)
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133
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134 # Get an item from the queue
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135 def _get(self):
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136 item = self.queue[0]
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137 del self.queue[0]
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138 return item