how to use python zipfile to append comment for a zip file?

Question

    $ echo "short"|zip -z test.zip
    enter new zip file comment (end with .):
    $ md5sum test.zip
    48da9079a2c19f9755203e148731dae9  test.zip
    $ echo "longlong"|zip -z test.zip
    current zip file comment is:
    short
    enter new zip file comment (end with .):
    $ md5sum test.zip
    3618846524ae0ce51fbc53e4b32aa35b  test.zip
    $ echo "short"|zip -z test.zip
    current zip file comment is:
    longlong
    enter new zip file comment (end with .):
    root@Debian:~# md5sum test.zip
    48da9079a2c19f9755203e148731dae9  test.zip
    $ echo "longlong"|zip -z test.zip
    current zip file comment is:
    short
    enter new zip file comment (end with .):
    $ md5sum test.zip
    3618846524ae0ce51fbc53e4b32aa35b  test.zip
    $
    $
    $ cat test.py
    #/usr/bin/env python
    #coding: utf-8

    import zipfile
    import subprocess

    zip_name = 'test.zip'

    def add_comment(zip_name, comment):
        with zipfile.ZipFile(zip_name, 'a') as zf:
            zf.comment = comment

    add_comment(zip_name, "short")
    print subprocess.Popen(['md5sum', zip_name], stdout=subprocess.PIPE).communicate()[0],
    add_comment(zip_name, "longlong")
    print subprocess.Popen(['md5sum', zip_name], stdout=subprocess.PIPE).communicate()[0],
    add_comment(zip_name, "short")
    print subprocess.Popen(['md5sum', zip_name], stdout=subprocess.PIPE).communicate()[0],
    add_comment(zip_name, "longlong")
    print subprocess.Popen(['md5sum', zip_name], stdout=subprocess.PIPE).communicate()[0],
    $
    $ python test.py 
    48da9079a2c19f9755203e148731dae9  test.zip
    3618846524ae0ce51fbc53e4b32aa35b  test.zip
    89c2038501f737991ca21aa097ea9956  test.zip
    3618846524ae0ce51fbc53e4b32aa35b  test.zip

At shell env, the fist time and the third time, "test.zip" md5 values are the same, the second time and the forth time, "test.zip" md5 values are the same, but when i use python zipfile, the result is not like that. How can I do this with the Python zipfile module?

Answer 1

The zipfile.ZipFile() class has a comment attribute you can set.

Open the file in append mode, alter the comment, and it'll be written out when closed:

from zipfile import ZipFile

with ZipFile('test.zip', 'a') as testzip:
    testzip.comment = 'short'

When you use a ZipFile as a context manager, like a regular file it'll automatically be closed when the with block is exited.