[Numpy-discussion] [ANN] python-blosc v1.2.5

Valentin Haenel valentin at haenel.co
Wed Apr 15 14:56:17 EDT 2015

Announcing python-blosc 1.2.5

What is new?

This release contains support for Blosc v1.5.4 including changes to how
the GIL is kept. This was required because Blosc was refactored in the
v1.5.x line to remove global variables and to use context objects
instead. As such, it became necessary to keep the GIL while calling
Blosc from Python code that uses the multiprocessing module.

In addition, is now possible to change the blocksize used by Blosc using
``set_blocksize``. When using this however, bear in mind that the
blocksize has been finely tuned to be a good default value and that
randomly messing with this value may have unforeseen and unpredictable
consequences on the performance of Blosc.

Additionally, we can now compile on Posix architectures, thanks again to
Andreas Schwab for that one.

For more info, you can have a look at the release notes in:


More docs and examples are available in the documentation site:


What is it?

Blosc (http://www.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.

Blosc is the first compressor that is meant not only to reduce the size
of large datasets on-disk or in-memory, but also to accelerate object
manipulations that are memory-bound
(http://www.blosc.org/docs/StarvingCPUs.pdf).  See
http://www.blosc.org/synthetic-benchmarks.html for some benchmarks on
how much speed it can achieve in some datasets.

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.

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

There is also a handy tool built on Blosc called Bloscpack
(https://github.com/Blosc/bloscpack). It features a commmand line
interface that allows you to compress large binary datafiles on-disk.
It also comes with a Python API that has built-in support for
serializing and deserializing Numpy arrays both on-disk and in-memory at
speeds that are competitive with regular Pickle/cPickle machinery.


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.


  **Enjoy data!**

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