# What’s new in h5py 3.6

## New features

- Pre-built packages are now available for Python 3.10.

## Deprecations

- Using `Dataset.astype()` as a context manager (`with dset.astype(t):`) is deprecated. Slice the object returned by astype instead (`data = dset.astype(t)[:10]`). This works from h5py 3.0 onwards.

- Getting the value of `h5py.get_config().default_file_mode` now issues a deprecation warning. This has been `'r'` by default from h5py 3.0, and cannot be changed since 3.3.

## Building h5py

- h5py now requires the `oldest-supported-numpy` package at build time, instead of maintaining its own list of the oldest supported NumPy versions. The effect should be similar, but hopefully more reliable.

## Development

- The custom `setup.py test` has been removed. tox should be used instead during development (see Run the tests), and `pytest --pyargs h5py` can be used to test h5py after installation.