[Python-Dev] LZMA compression support in 3.3 (original) (raw)

Terry Reedy tjreedy at udel.edu
Sat Aug 27 21:47:00 CEST 2011

On 8/27/2011 9:47 AM, Nadeem Vawda wrote:

I'd like to propose the addition of a new module in Python 3.3. The 'lzma' module will provide support for compression and decompression using the LZMA algorithm, and the .xz and .lzma file formats. The matter has already been discussed on the tracker<http://bugs.python.org/issue6715>, where there seems to be a consensus that this is a desirable feature. What are your thoughts?

As I read the discussion, the idea has been more or less accepted in principle. However, the current patch is not and needs changes.

The proposed module's API will be very similar to that of the bz2 module; the only differences will be additional keyword arguments to some functions, for specifying container formats and detailed compressor options.

I believe Antoine suggested a PEP. It should summarize the salient points in the long tracker discussion into a coherent exposition and flesh out the details implied above. (Perhaps they are already in the proposed doc addition.)

The implementation will also be similar to bz2 - basic compressor and decompressor classes written in C, with convenience functions and a file interface implemented on top of those in Python.

I would follow Martin's suggestions, including doing all i/o with the io module and the following: "So I would propose that a very thin C layer is created around the C library that focuses on the actual algorithms, and that any higher layers (in particular file formats) are done in Python."

If we minimize the C code we add and maximize what is done in Python, that would maximize the ease of porting to other implementations. This would conform to the spirit of PEP 399.

-- Terry Jan Reedy

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