This is a fork from this ticket: http://bugs.python.org/issue21404

tarfile has a compression level and seems to get now the missing documentation for it. But there is still a compression level missing for zipfile.

btw. hacked work-a-round is:

    zlib.Z_DEFAULT_COMPRESSION = 9

Would compresslevel be a suitable argument? All the backend compressors accept values from 1 to 9 if I'm not mistaken.

Yes, it would make sence or better yet have a arg that is optional that if not set make it = ``9``.

I thought about that, but:

1. compresslevel=None might make look like no compression was being done at all
2. The current default is not 9 for all backends

New changeset ce237c7d58ba207575cdfb0195a58a6407fbf717 by Gregory P. Smith (Bo Bayles) in branch 'master':
bpo-21417: Add compresslevel= to the zipfile module (GH-5385)
https://github.com/python/cpython/commit/ce237c7d58ba207575cdfb0195a58a6407fbf717

I have a concern about the _compresslevel attribute of ZipInfo. Why is it underscored and not documented?

I made a comment about that in the pull request that went unchallenged ([1]), but I'm happy to change it.

[1] https://github.com/python/cpython/pull/5385#pullrequestreview-92055354

keeping the conversation in one place, the code review comment was: "I've prefixed this with an underscore because it's not exposed when reading back. ZipInfo has another "private" attribute, _raw_time"

compresslevel is documented on the public APIs where it appears, I do not believe it needs to be a public attribute within ZipInfo given the above as that is an implementation detail.  If we ever find a good reason to make it public in the future we can add a property.

This makes sense to me. Thank you for explanation.