What’s new in h5py 3.7¶

New features¶

Both Apple Silicon (arm64) and Intel (x86_64) Mac wheels are now provided (PR 2065). Apple Silicon wheels are not automatically tested, however, as we’re not aware of any CI offerings that do this.
Provide the ability to use the Direct Virtual File Driver (VFD) from HDF5 (Linux only). If the Direct VFD driver is present at the time of compilation, users can use the Direct VFD by passing the keyword argument driver="direct" to the h5py.File constructor.

To use the Direct VFD, HDF5 and h5py must have both been compiled with this enabled. Currently, pre-built h5py wheels on PyPI do not include the Direct VFD. Other packages such as the conda package on conda-forge might include it. Alternatively, you can build h5py from source against an HDF5 build with the direct driver enabled.
The File constructor contains two new parameters alignment_threshold, and alignment_interval controling the data alignment within the HDF5 file (PR 2040).
create_dataset() and require_dataset() now accept parameters efile_prefix and virtual_prefix to set a filesystem path prefix to use to find files for external datasets and for virtual dataset sources (PR 2092). These only affect the current access; the prefix is not stored in the file.
h5py wheels on PyPI now bundle HDF5 version 1.12.2 (PR 2099).
h5py Mac wheels on PyPI now bundle zlib version 1.2.12 (PR 2082).
Pre-built wheels are now available for Python 3.10 on Linux ARM64 (PR 2094).

Fix a deadlock which was possible when the same dataset was accessed from multiple threads (GH2064).
New attributes are created directly, instead of via a temporary attribute with subsequent renaming. This fixes overwriting attributes with track_order=True.
Fix for building with mpi4py on Python 3.10 (PR 2101).
Fixed fancy indexing with a boolean array for a single dimension (PR 2079).
Avoid returning unitialised memory when reading from a chunked dataset with missing chunks and no fill value (PR 2076).
Enable setting of fillvalue for datasets with variable length string dtype (PR 2044).
Closing a file or calling get_obj_ids() no longer re-enables Python garbage collection if it was previously disabled (PR 2020).