Function slice_array

dask/array/slicing.py:101–175

Main function for array slicing This function makes a new dask that slices blocks along every dimension and aggregates (via cartesian product) each dimension's slices so that the resulting block slices give the same results as the original slice on the original structure I

(out_name, in_name, blockdims, index)

@disable_gc()
def slice_array(out_name, in_name, blockdims, index):
    """
    Main function for array slicing

    This function makes a new dask that slices blocks along every
    dimension and aggregates (via cartesian product) each dimension's
    slices so that the resulting block slices give the same results
    as the original slice on the original structure

    Index must be a tuple.  It may contain the following types

        int, slice, list (at most one list), None

    Parameters
    ----------
    in_name - string
      This is the dask variable name that will be used as input
    out_name - string
      This is the dask variable output name
    blockshape - iterable of integers
    index - iterable of integers, slices, lists, or None

    Returns
    -------
    Dict where the keys are tuples of

        (out_name, dim_index[, dim_index[, ...]])

    and the values are

        (function, (in_name, dim_index, dim_index, ...),
                   (slice(...), [slice()[,...]])

    Also new blockdims with shapes of each block

        ((10, 10, 10, 10), (20, 20))

    Examples
    --------
    >>> from pprint import pprint
    >>> dsk, blockdims = slice_array('y', 'x', [(20, 20, 20, 20, 20)],
    ...                              (slice(10, 35),))
    >>> pprint(dsk)  # doctest: +ELLIPSIS +NORMALIZE_WHITESPACE
    {('y', 0): <Task ('y', 0) getitem(TaskRef(('x', 0)), (slice(10, 20, 1),))>,
     ('y', 1): <Task ('y', 1) getitem(TaskRef(('x', 1)), (slice(0, 15, 1),))>}
    >>> blockdims
    ((10, 15),)

    See Also
    --------
    This function works by successively unwrapping cases and passing down
    through a sequence of functions.

    slice_with_newaxis : handle None/newaxis case
    slice_wrap_lists : handle fancy indexing with lists
    slice_slices_and_integers : handle everything else
    """
    blockdims = tuple(map(tuple, blockdims))