[Numpy-discussion] ANN: python-blosc 1.1 (final) released

Francesc Alted francesc at continuum.io
Fri May 24 08:08:34 EDT 2013

Announcing python-blosc 1.1

What is it?

python-blosc (http://blosc.pydata.org/) is a Python wrapper for the
Blosc compression library.

Blosc (http://blosc.org) is a high performance compressor optimized for
binary data.  It has been designed to transmit data to the processor
cache faster than the traditional, non-compressed, direct memory fetch
approach via a memcpy() OS call.  Whether this is achieved or not
depends of the data compressibility, the number of cores in the system,
and other factors.  See a series of benchmarks conducted for many
different systems: http://blosc.org/trac/wiki/SyntheticBenchmarks.

Blosc works well for compressing numerical arrays that contains data
with relatively low entropy, like sparse data, time series, grids with
regular-spaced values, etc.

There is also a handy command line for Blosc called Bloscpack
(https://github.com/esc/bloscpack) that allows you to compress large
binary datafiles on-disk.  Although the format for Bloscpack has not
stabilized yet, it allows you to effectively use Blosc from your
favorite shell.

What is new?

- Added new `compress_ptr` and `decompress_ptr` functions that allows to
   compress and decompress from/to a data pointer, avoiding an
   itermediate copy for maximum speed.  Be careful, as these are low
   level calls, and user must make sure that the pointer data area is

- Since Blosc (the C library) already supports to be installed as an
   standalone library (via cmake), it is also possible to link
   python-blosc against a system Blosc library.

- The Python calls to Blosc are now thread-safe (another consequence of
   recent Blosc library supporting this at C level).

- Many checks on types and ranges of values have been added.  Most of
   the calls will now complain when passed the wrong values.

- Docstrings are much improved. Also, Sphinx-based docs are available

Many thanks to Valentin Hänel for his impressive work for this release.

For more info, you can see the release notes in:


More docs and examples are available in the documentation site:



python-blosc is in PyPI repository, so installing it is easy:

$ pip install -U blosc  # yes, you should omit the python- prefix

Download sources

The sources are managed through github services at:



There is Sphinx-based documentation site at:


Mailing list

There is an official mailing list for Blosc at:

blosc at googlegroups.com


Both Blosc and its Python wrapper are distributed using the MIT license.


for more details.


Francesc Alted

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