array-api-extra¶

This is a library housing “array-agnostic” implementations of functions built on top of the Python array API standard.

The intended users of this library are “array-consuming” libraries which are using array-api-compat to make their own library’s functions array-agnostic. In this library, they will find a set of tools which provide extra functionality on top of the array API standard, which other array-consuming libraries in a similar position have found useful themselves.

It is currently used by:

SciPy - Fundamental algorithms for scientific computing.
…

Installation¶

array-api-extra is available on PyPI:

python -m pip install array-api-extra

And on conda-forge:

mamba install array-api-extra
# or
pixi add array-api-extra

Warning

This library currently provides no backwards-compatibility guarantees! If you require stability, it is recommended to pin array-api-extra to a specific version, or vendor the library inside your own.

Note

This library depends on array-api-compat. We aim for compatibility with the latest released version of array-api-compat, and your mileage may vary with older or dev versions.

Vendoring¶

To vendor the library, clone the array-api-extra repository and copy it into the appropriate place in your library, like:

cp -a array-api-extra/src/array_api_extra mylib/vendored/

array-api-extra depends on array-api-compat. You may either add a dependency in your own project to array-api-compat or vendor it too:

Clone the array-api-compat repository and copy it next to your vendored array-api-extra:
```
cp -a array-api-compat/array_api_compat mylib/vendored/
```
Create a new hook file which array-api-extra will use instead of the top-level array-api-compat if present:
```
echo 'from mylib.vendored.array_api_compat import *' > mylib/vendored/_array_api_compat_vendor.py
```

This also allows overriding array-api-compat functions if you so wish. E.g. your mylib/vendored/_array_api_compat_vendor.py could look like this:

from mylib.vendored.array_api_compat import *
from mylib.vendored.array_api_compat import array_namespace as _array_namespace_orig


def array_namespace(*xs, **kwargs):
    import mylib

    if any(isinstance(x, mylib.MyArray) for x in xs):
        return mylib
    else:
        return _array_namespace_orig(*xs, **kwargs)

Usage¶

Typical usage of this library looks like:

import array_api_extra as xpx

...
xp = array_namespace(x)
y = xp.sum(x)
...
return xpx.atleast_nd(y, ndim=2, xp=xp)

Note

Functions in this library assume input arrays are arrays (not “array-likes”) and that the namespace passed as xp (if given) is compatible with the standard - this means that it should come from array-api-compat’s array_namespace, or otherwise be compatible with the standard.

Calling functions without providing an xp argument means that array_namespace is called internally to determine the namespace.

In the examples shown in the docstrings of functions from this library, array-api-strict is used as the array namespace xp. In reality, code using this library will be written to work with any compatible array namespace as xp, not any particular implementation.

Some functions may only work with array libraries supported by array-api-compat. This will be clearly indicated in the docs.

Scope¶

Functions that are in-scope for this library will:

Implement functionality which does not already exist in the array API standard.
Implement functionality which may be generally useful across various libraries.
Be implemented with type annotations and numpydoc-style docstrings.
Be tested against array-api-strict.

Functions are implemented purely in terms of the array API standard where possible. Where functions must use library-specific helpers for libraries supported by array-api-compat, this will be clearly marked in their API reference page.

In particular, the following kinds of function are also in-scope:

Functions which implement array API standard extension functions in terms of functions from the base standard.
Functions which add functionality (e.g. extra parameters) to functions from the standard.

The following features are currently out-of-scope for this library:

Delegation to known, existing array libraries (unless necessary).
- It is quite simple to wrap functions in this library to also use existing implementations. Such delegation will not live in this library for now, but the array-agnostic functions in this library could form an array-agnostic backend for such delegating functions in the future, here or elsewhere.
Functions which accept “array-like” input, or standard-incompatible namespaces.
- It is possible to prepare input arrays and a standard-compatible namespace via array-api-compat downstream in consumer libraries.
Functions which are specific to a particular domain.
- These functions may belong better in an array-consuming library which is specific to that domain.