16

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?

MiB_Coder
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2 Answers2

29

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()
Charles Duffy
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    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. – Pete Jul 05 '17 at 12:15
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    @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. – Charles Duffy Jul 05 '17 at 13:51
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)
Jaakko
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