HDF5 for Python 1.0
h5py at alfven.org
Mon Dec 1 22:22:16 CET 2008
Announcing HDF5 for Python (h5py) 1.0
What is h5py?
HDF5 for Python (h5py) is a general-purpose Python interface to the
Hierarchical Data Format library, version 5. HDF5 is a versatile,
mature scientific software library designed for the fast, flexible
storage of enormous amounts of data.
>From a Python programmer's perspective, HDF5 provides a robust way to
store data, organized by name in a tree-like fashion. You can create
datasets (arrays on disk) hundreds of gigabytes in size, and perform
random-access I/O on desired sections. Datasets are organized in a
filesystem-like hierarchy using containers called "groups", and
accesed using the tradional POSIX /path/to/resource syntax.
This is the fourth major release of h5py, and represents the end
of the "unstable" (0.X.X) design phase.
Why should I use it?
H5py provides a simple, robust read/write interface to HDF5 data
from Python. Existing Python and NumPy concepts are used for the
interface; for example, datasets on disk are represented by a proxy
class that supports slicing, and has dtype and shape attributes.
HDF5 groups are are presented using a dictionary metaphor, indexed
A major design goal of h5py is interoperability; you can read your
existing data in HDF5 format, and create new files that any HDF5-
aware program can understand. No Python-specific extensions are
used; you're free to implement whatever file structure your application
Almost all HDF5 features are available from Python, including things
like compound datatypes (as used with NumPy recarray types), HDF5
attributes, hyperslab and point-based I/O, and more recent features
in HDF 1.8 like resizable datasets and recursive iteration over entire
The foundation of h5py is a near-complete wrapping of the HDF5 C API.
HDF5 identifiers are first-class objects which participate in Python
reference counting, and expose the C API via methods. This low-level
interface is also made available to Python programmers, and is
See the Quick-Start Guide for a longer introduction with code examples:
Where to get it
* Main website, documentation: http://h5py.alfven.org
* Downloads, bug tracker: http://h5py.googlecode.com
* The HDF group website also contains a good introduction:
* UNIX-like platform (Linux or Mac OS-X); Windows version is in
* Python 2.5 or 2.6
* NumPy 1.0.3 or later (1.1.0 or later recommended)
* HDF5 1.6.5 or later, including 1.8. Some features only available
when compiled against HDF5 1.8.
* Optionally, Cython (see cython.org) if you want to use custom install
options. You'll need version 0.9.8.1.1 or later.
About this version
Version 1.0 follows version 0.3.1 as the latest public release. The
major design phase (which began in May of 2008) is now over; the design
of the high-level API will be supported as-is for the rest of the 1.X
series, with minor enhancements.
This is the first version to support Python 2.6, and the first to use
Cython for the low-level interface. The license remains 3-clause BSD.
** This project is NOT affiliated with The HDF Group. **
Thanks to D. Dale, E. Lawrence and other for their continued support
and comments. Also thanks to the PyTables project, for inspiration
and generously providing their code to the community, and to everyone
at the HDF Group for creating such a useful piece of software.
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