pyunixlzw

pyunixlzw is a "pure" python3 implementation of the Unix compress/uncompress tool.

Usage

pyunixlzw comes with access to both a module and a script that serves as a semi-replacement for (N)compress.

Module

>>> import pyunixlzw
>>> print(pyunixlzw.compress(b'aaaaaaaaaa'))
b'\x1f\x9d\x90a\x02\n\x1c\x08'
>>> print(pyunixlzw.decompress(b'\x1f\x9d\x90a\x02\n\x1c\x08'))
b'aaaaaaaaaa'

Script

$ pyunixlzw -h
usage: pyunixlzw [-h] [-d] [-c] [-b MAXBITS] [-f] [-v] [-V] file

A pure-Python3 implementation of UNIX compress and decompress.

positional arguments:
  file

options:
  -h, --help            show this help message and exit
  -d, --decompress      If given, decompression is done instead.
  -c, --stdout          Write output on stdout, don't remove original.
  -b, --maxbits MAXBITS
                        Parameter limits the max number of bits/code.
  -f, --force           Forces output file to be generated, even if one already exists, and even if no space is saved
                        by compressing.
  -v, --stats           Write compression statistics.
  -V, --version         Output version and author.
$ 

Installation

pip install pyunixlzw

WARNING

The compression function attempts to mirror (N)compress as close as possible, but there are times that a file compressed with compress will not match the output of a file compressed with pyunixlzw. This is due to logic that determines when to output a CLEAR code, which I was unable to replicate in my script.

These mismatched files can still be handled with both (N)compress and pyunixlzw; the primary difference is that (N)compress offers a much better compression ratio in much more efficient logic.

If anyone is able to integrate the CLEAR code logic, feel free to submit a note or pull request replacing the check_clear function contents in compress.py with the logic required to match.