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annotate roundup/cgi/ZTUtils/Batch.py @ 1049:b9988e118055

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author Richard Jones <richard@users.sourceforge.net>
date Thu, 05 Sep 2002 00:37:09 +0000
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children c26471971d18
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1049
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1 ##############################################################################
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2 #
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3 # Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
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4 #
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5 # This software is subject to the provisions of the Zope Public License,
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6 # Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
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7 # THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
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8 # WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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9 # WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
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10 # FOR A PARTICULAR PURPOSE
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11 #
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12 ##############################################################################
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13 __doc__='''Batch class, for iterating over a sequence in batches
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14
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15 $Id: Batch.py,v 1.1 2002-09-05 00:37:09 richard Exp $'''
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16 __version__='$Revision: 1.1 $'[11:-2]
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17
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18 class LazyPrevBatch:
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19 def __of__(self, parent):
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20 return Batch(parent._sequence, parent._size,
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21 parent.first - parent._size + parent.overlap, 0,
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22 parent.orphan, parent.overlap)
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23
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24 class LazyNextBatch:
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25 def __of__(self, parent):
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26 try: parent._sequence[parent.end]
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27 except IndexError: return None
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28 return Batch(parent._sequence, parent._size,
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29 parent.end - parent.overlap, 0,
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30 parent.orphan, parent.overlap)
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31
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32 class LazySequenceLength:
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33 def __of__(self, parent):
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34 parent.sequence_length = l = len(parent._sequence)
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35 return l
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36
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37 class Batch:
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38 """Create a sequence batch"""
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39 __allow_access_to_unprotected_subobjects__ = 1
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40
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41 previous = LazyPrevBatch()
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42 next = LazyNextBatch()
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43 sequence_length = LazySequenceLength()
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44
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45 def __init__(self, sequence, size, start=0, end=0,
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46 orphan=0, overlap=0):
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47 '''Encapsulate "sequence" in batches of "size".
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48
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49 Arguments: "start" and "end" are 0-based indexes into the
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50 sequence. If the next batch would contain no more than
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51 "orphan" elements, it is combined with the current batch.
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52 "overlap" is the number of elements shared by adjacent
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53 batches. If "size" is not specified, it is computed from
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54 "start" and "end". Failing that, it is 7.
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55
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56 Attributes: Note that the "start" attribute, unlike the
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57 argument, is a 1-based index (I know, lame). "first" is the
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58 0-based index. "length" is the actual number of elements in
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59 the batch.
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60
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61 "sequence_length" is the length of the original, unbatched, sequence
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62 '''
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63
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64 start = start + 1
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65
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66 start,end,sz = opt(start,end,size,orphan,sequence)
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67
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68 self._sequence = sequence
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69 self.size = sz
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70 self._size = size
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71 self.start = start
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72 self.end = end
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73 self.orphan = orphan
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74 self.overlap = overlap
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75 self.first = max(start - 1, 0)
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76 self.length = self.end - self.first
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77 if self.first == 0:
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78 self.previous = None
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79
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80
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81 def __getitem__(self, index):
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82 if index < 0:
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83 if index + self.end < self.first: raise IndexError, index
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84 return self._sequence[index + self.end]
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85
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86 if index >= self.length: raise IndexError, index
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87 return self._sequence[index+self.first]
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88
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89 def __len__(self):
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90 return self.length
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91
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92 def opt(start,end,size,orphan,sequence):
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93 if size < 1:
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94 if start > 0 and end > 0 and end >= start:
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95 size=end+1-start
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96 else: size=7
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97
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98 if start > 0:
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99
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100 try: sequence[start-1]
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101 except IndexError: start=len(sequence)
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102
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103 if end > 0:
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104 if end < start: end=start
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105 else:
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106 end=start+size-1
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107 try: sequence[end+orphan-1]
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108 except IndexError: end=len(sequence)
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109 elif end > 0:
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110 try: sequence[end-1]
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111 except IndexError: end=len(sequence)
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112 start=end+1-size
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113 if start - 1 < orphan: start=1
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114 else:
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115 start=1
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116 end=start+size-1
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117 try: sequence[end+orphan-1]
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118 except IndexError: end=len(sequence)
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119 return start,end,size
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