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Batcher 2

Cut sliceable objects into batches, eg for paging display on a website

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Batcher
-------

Splits any sliceable object into batches::

        >>> from batcher import Batcher
        >>> items = list('ABCDEFGHIJ')
        >>> batcher = Batcher(items, 4)
        >>> # How many batches are available?
        >>> len(batcher)
        3
        >>> # Get contents of the first batch
        >>> list(batcher[0])
        ['A', 'B', 'C', 'D']

Batches look like lists but know about their context too::

        >>> batch = batcher[1]
        >>> batch
        
        >>> batcher[1].previous
        
        >>> batcher[1].next
        
        >>> batcher[2].next
        None

A common requirement in web applications is to implement a pager widget.
The range method can help when the user is viewing page **n** and we want to
display a range of pages centered on **n**, adjusting endpoints to keep
them in range::

        >>> items = range(100)
        >>> batcher = Batcher(items, 4)
        >>> len(batcher)
        25
        >>> # The range of 5 batches centered on the given batch
        >>> batcher[0].range(5)
        [, , , , ]
        >>> batcher[7].range(5)
        [, , , , ]
        >>> batcher[23].range(5)
        [, , , , ]

If there aren't enough batches available, the entire batch will be returned::

        >>> items = range(10)
        >>> batcher = Batcher(items, 4)
        >>> len(batcher)
        3
        >>> batcher[1].range(5)
        [, , ]

Because batches use python's slicing API to retrieve data, we can
interrogate the slice object to find out the indices of the first and last
items in a batch, useful for showing data such as "Page 1 (items 1-10)"::

        >>> items = range(25)
        >>> batcher = Batcher(items, 10)
        >>> batch = batcher[0]
        >>> batch.slice
        slice(0, 10, None)
        >>> "Page %d (items %d-%d)" % (batch.index + 1, batch.slice.start + 1,
batch.slice.stop)
        'Page 1 (items 1-10)'

Note how python's slice semantics mean that the indices are zero-based (so
we add 1 when formatting for display) and that the stop index of the slice
points to the item after the end of the series.
 
File Type Py Version Uploaded on Size # downloads
Batcher-2.tar.gz (md5) Source 2009-12-15 8KB 539