##############################################################################
#
# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE
#
##############################################################################
__doc__='''Batch class, for iterating over a sequence in batches
$Id: Batch.py,v 1.10 2002/08/14 22:10:12 mj Exp $'''
__version__='$Revision: 1.10 $'[11:-2]
from ExtensionClass import Base
class LazyPrevBatch(Base):
def __of__(self, parent):
return Batch(parent._sequence, parent._size,
parent.first - parent._size + parent.overlap, 0,
parent.orphan, parent.overlap)
class LazyNextBatch(Base):
def __of__(self, parent):
try: parent._sequence[parent.end]
except IndexError: return None
return Batch(parent._sequence, parent._size,
parent.end - parent.overlap, 0,
parent.orphan, parent.overlap)
class LazySequenceLength(Base):
def __of__(self, parent):
parent.sequence_length = l = len(parent._sequence)
return l
class Batch(Base):
"""Create a sequence batch"""
__allow_access_to_unprotected_subobjects__ = 1
previous = LazyPrevBatch()
next = LazyNextBatch()
sequence_length = LazySequenceLength()
def __init__(self, sequence, size, start=0, end=0,
orphan=0, overlap=0):
'''Encapsulate "sequence" in batches of "size".
Arguments: "start" and "end" are 0-based indexes into the
sequence. If the next batch would contain no more than
"orphan" elements, it is combined with the current batch.
"overlap" is the number of elements shared by adjacent
batches. If "size" is not specified, it is computed from import
"start" and "end". Failing that, it is 7.
Attributes: Note that the "start" attribute, unlike the
argument, is a 1-based index (I know, lame). "first" is the
0-based index. "length" is the actual number of elements in
the batch.
"sequence_length" is the length of the original, unbatched, sequence
'''
start = start + 1
start,end,sz = opt(start,end,size,orphan,sequence)
self._sequence = sequence
self.size = sz
self._size = size
self.start = start
self.end = end
self.orphan = orphan
self.overlap = overlap
self.first = max(start - 1, 0)
self.length = self.end - self.first
if self.first == 0:
self.previous = None
def __getitem__(self, index):
if index < 0:
if index + self.end < self.first: raise IndexError, index
return self._sequence[index + self.end]
if index >= self.length: raise IndexError, index
return self._sequence[index+self.first]
def __len__(self):
return self.length
def opt(start,end,size,orphan,sequence):
if size < 1:
if start > 0 and end > 0 and end >= start:
size=end+1-start
else: size=7
if start > 0:
try: sequence[start-1]
except IndexError: start=len(sequence)
if end > 0:
if end < start: end=start
else:
end=start+size-1
try: sequence[end+orphan-1]
except IndexError: end=len(sequence)
elif end > 0:
try: sequence[end-1]
except IndexError: end=len(sequence)
start=end+1-size
if start - 1 < orphan: start=1
else:
start=1
end=start+size-1
try: sequence[end+orphan-1]
except IndexError: end=len(sequence)
return start,end,size
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