vector_structure

Lightweight utilities for working with structured flat vectors and block matrices in NumPy.

class vector_structure.VectorStructure(sizes: Sequence[tuple[BlockName, int]])

Helper class to describe block vectors and block matrices.

cuts

dict[BlockName, slice] – the indices for each named block

size

int – the total size of the described vector

__getitem__(idx: BlockName | tuple[BlockName, ...] | slice) → slice

Get the indices for one or multiple blocks.

Example

>>> from vector_structure import VectorStructure
>>> x = VectorStructure([("x", 3), ("y", 2), ("z", 1)])
>>> li = [1, 2, 3, 4, 5, 6]
>>> li[x["y"]]
[4, 5]
>>> li[x["y":"z"]]
[4, 5, 6]
>>> li[x["x","y"]]
[1, 2, 3, 4, 5]

Note

when indexing by slice, both the start and the stop are included, i.e. a[“a”:”c”] = a[“a”, “b”, “c”]. This is different from the Python convention, but similar to Pandas.

__init__(sizes: Sequence[tuple[BlockName, int]])

__repr__()

Return repr(self).

__weakref__

list of weak references to the object (if defined)

as_dict(arr: SpecificArrayLike) → dict[BlockName, SpecificArrayLike]

Split the array into pieces according to the vector structure.

Inverse operation to from_dict().

Example

>>> from vector_structure import VectorStructure
>>> x = VectorStructure([("x", 3), ("y", 1)])
>>> x.as_dict([1, 2, 3, 4])
{'x': [1, 2, 3], 'y': [4]}

block_size(idx: BlockName | tuple[BlockName, ...] | slice) → int

Return the size of one or more blocks.

Parameters:

idx – Index. See __getitem__().

This is just syntactic sugar for simple_slice_len(self[idxs])

from_dict(di: dict[BlockName, SpecificArrayLike]) → SpecificArrayLike

Join an array from pieces.

Inverse operation to as_dict().

Example

>>> x = VectorStructure([("x", 3), ("y", 1)])
>>> x.from_dict({"x": [1, 2, 3], "y": [4]})
[1, 2, 3, 4]

vector_structure.simple_slice_len(sl: slice) → int

Compute the size of a ‘simple’ slice.

A ‘simple’ slice is a slice with (step=None or step=1) and start >= 0 and stop >= 0. VectorStructure[…] always returns simple slices. This function is just syntactic sugar for sl.stop - sl.start.

Parameters:

sl – “Simple” slice

Raises:

ValueError – If the slice is not a “simple” slice.

Returns:

The length of the slice, i.e. len(li[sl]) for a container li.