parse_assignment_indices(indices, shape)

The aim of this is to convert the indices to a standardised form so that it is easier to ascertain which chunks are touched by the indices.

This function is intended to be called by setitem_array .

A slice object that is decreasing (i.e. with a negative step), is recast as an increasing slice (i.e. with a postive step. For example slice(7,3,-1) would be cast as slice(4,8,1) . This is to facilitate finding which blocks are touched by the index. The dimensions for which this has occured are returned by the function.

Parameters

indices : numpy-style indices

Indices to array defining the elements to be assigned.

shape : sequence of `int`

The shape of the array.

Returns

parsed_indices : `list`

The reformated indices that are equivalent to the input indices.

indices_shape : `list`

The shape implied by of the parsed indices. For instance, indices of (slice(0,2), 5, [4,1,-1]) will have shape [2,3] .

reverse : `list`

The positions of the dimensions whose indices in the parsed_indices output are reversed slices.

Reformat the indices for assignment.

Examples

This example is valid syntax, but we were not able to check execution

>>> parse_assignment_indices((slice(1, -1),), (8,))
([slice(1, 7, 1)], [6], [])

This example is valid syntax, but we were not able to check execution

>>> parse_assignment_indices(([1, 2, 6, 5],), (8,))
([array([1, 2, 6, 5])], [4], [])

This example is valid syntax, but we were not able to check execution

>>> parse_assignment_indices((3, slice(-1, 2, -1)), (7, 8))
([3, slice(3, 8, 1)], [5], [1])

See :

Back References

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dask.array.slicing.parse_assignment_indices

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