Currently zlib.compress allow only positional arguments. For code readability reasons i think that we should allow the level argument to be keyword argument. Now when someone uses zlib.compress he will be able to do zlib.compess(some_data, level=7) instead of zlib.compress(some_data, 7).

There is a patch included with the change.

Seems like a reasonable enhancement. A couple of points:

* Watch out for the parameter names. Should it be “bytes” or “data”?
* Z_DEFAULT_COMPRESSION is -1 not 6 (see Issue 26244)
* Needs a version changed notice, and probably a What’s New update

Thanks for the review.
1. Changed "bytes" to "data".
2. Updated Doc as in issue 26244 (will update the patch if there will be changes there).
3. Added version changed notice but i don't think there is a need for What's new update.

Thanks, it looks good to me. I think “data” is a better name than “bytes”.

About What’s New, I thought the general idea was to document all enhancements, though I admit this is about as small as they come. There is precedent with the compile() builtin (Issue 1444529, Python 2.6), although there is no indication of kwargs in the main documentation for compile(). But on the other hand, str.split() didn’t get any What’s New entry (Issue 14081, Python 3.3). See also <https://docs.python.org/devguide/committing.html#what-s-new-and-news-entries>.

There is an outdated patch in issue 16764 for zlib.compress(), zlib.decompress(), zlib.flush() and other functions. Perhaps we can close it as a duplicate of this one.

The patch at Issue 16764 has a test case for the new level=... keyword. Perhaps you would like to incorporate/update it :)

Added the "suggested" test

New changeset 592db8704d38 by Martin Panter in branch 'default':
Issue #26243: zlib.compress() keyword argument support by Aviv Palivoda
https://hg.python.org/cpython/rev/592db8704d38

New changeset dc758f51b8f5 by Martin Panter in branch 'default':
Issue 26243: Forgot to update zlib doc strings in Argument Clinic
https://hg.python.org/cpython/rev/dc758f51b8f5

I did add a What’s New entry (I hope nobody minds), and updated the doc strings in the zlib module. Thanks for the work on this Aviv.

The original request was for supporting level as keyword argument. Making the first argument a keyword argument was unintentional side effect (due a to the limitation of argument parsing functions). Now it is possible to support positional-only and keyword arguments in one function (see issue26282). Proposed patch makes the first argument positional-only again.

Regenerated for review.

The patch (with Berker’s fix) looks okay. Personally, I don’t see a big problem with the first argument also having a keyword name, but I don’t mind if it doesn’t either.

New changeset 01f82a7a1250 by Serhiy Storchaka in branch 'default':
Issue #26243: Only the level argument to zlib.compress() is keyword argument
https://hg.python.org/cpython/rev/01f82a7a1250

New changeset ab2e7e51869d by Serhiy Storchaka in branch 'default':
Issue #26243: Correct a wording in docs.
https://hg.python.org/cpython/rev/ab2e7e51869d

Thanks Berker and Martin.