# What’s new in h5py 3.13

## New features

- New `File.in_memory()` constructor to conveniently build an HDF5 file structure in memory (PR 2517).

- `Dataset` views returned by `astype()`, `asstr()` and `fields()` have gained the `.dtype`, `.ndim`, `.shape`, and `.size` attributes (PR 2550).

- The bundled HDF5 library in the pre-built packages was updated to 1.14.6 (PR 2554).

- Opening an existing dataset in a file is faster since it now only loads the “dataset creation property list” when required (PR 2552).

## Exposing HDF5 functions

- `H5Sselect_shape_same` exposed as `h5py.h5s.SpaceID.select_shape_same()` (PR 2529).

## Bug fixes

- Fix various bugs when applying `np.array` or `np.asarray` to a `Dataset` view returned by `astype()`, `asstr()`, or `fields()`.

## Building h5py

- Fixed building h5py with Numpy 2.3 (PR 2556).

- Bump the specified mpi4py version to fix building with MPI support on Python 3.13 (PR 2524).

- Fix for running `api_gen.py` directly (PR 2534).