How to unpack xz file with python which contains only data but no filename?

Question

I have a file, which I can decompress under linux using the following command:

unxz < file.xz > file.txt

How can I do the same using python? If I use python3 and the tarfile module and do the following:

import sys
import tarfile
try:
    with tarfile.open('temp.xz', 'r:xz') as t:
        t.extract()
except Exception as e:
    print("Error:", e.strerror)

I get the exception: ReadError('invalid header',). So apparently it expects some file- or directory information which is not present in the xz file.

So how can I decompress a file without header information?

Holdup

Answer 1

The tarfile module is only for... err... tar files. What you have here is not one.

---

XZ support is available in Python 3.3's LZMA module. In Python 2.x, you need backports.lzma.

try:
    import lzma
except ImportError:
    from backports import lzma

print lzma.open('file.xz').read()

Outreach

this gives me the data in binary format. is there a quick way to decompress a whole file? for example, I have a file "test.txt.xz" and need a command to get "test.txt". one way is to convert the data in binary format to utf-8 using this way: binary_data_buffer = lzma.open('test.txt.xz').read() , then string_buffer = binary_data_buffer.decode('utf-8') and finally write it to a file. but I'm pretty sure there is a more elegant way to do this. – Myosin

@Pete, lzma.open('test.txt.xz').read().decode('utf-8') is too much of a mouthful? That said, you can pass lzma.open('test.txt.xz', mode='rt', encoding='utf-8') to get multi-byte character decoding out-of-the-box. – Outreach

Answer 2

As noted by Charles in earlier comment,

Reading XZ-compressed text file in Python can be done with following (https://docs.python.org/3/library/lzma.html#lzma.open)

with lzma.open('test.txt.xz', mode='rt', encoding='utf-8') as fid:
    for line in fid:
        print(line)

Roadhouse