sqlite-3.25 now includes window functions, something very important in modern SQL.

 https://www.sqlite.org/windowfunctions.html

Could it be included in next Python maintenance release ?

To completely do this requires two things:

1) Upgrade SQLite included in a number of binary distributions

2) Update the sqlite extension to allow creating custom window functions in Python

The latter is definitely something that cannot be done in a maintenance release. The former is up to the release managers.

hum. On Windows at least, just drop-in replace the sqlite3.dll per the new sqlite-3.25 dll and the window functions just works.
==> I don't see the need for your latter point, at least on Windows.

checked with sqlite_bro on Python-3.6.7rc1 with example:
CREATE TABLE t2(a, b);
INSERT INTO t2 VALUES('a', 'one'), 
                     ('a', 'two'), 
                     ('a', 'three'), 
                     ('b', 'four'), 
                     ('c', 'five'), 
                     ('c', 'six');
SELECT a                        AS a,
       row_number() OVER win    AS row_number,
       rank() OVER win          AS rank,
       dense_rank() OVER win    AS dense_rank,
       percent_rank() OVER win  AS percent_rank,
       cume_dist() OVER win     AS cume_dist
FROM t2
WINDOW win AS (ORDER BY a);

My latter points makes it possible to define custom windowing functions in Python, similar to how it is already possible to define other SQLite functions in Python.

Due to the SQLite "Magellan" bug, I'd suggest this be 3.26+.

Details: https://blade.tencent.com/magellan/index_en.html
See also: https://bugs.python.org/issue35360

Issue 35360 will cover updating our Windows and macOS installers. I'm retargeting this issue to add a create_window_function() method to the Connection object. I already have a WIP branch and am going to submit a PR later this weekend.

I've implemented this in a fork / standalone packaging of the Python 3.x sqlite3 module. You can find the relevant portions (and a couple unrelated changes) in this commit:

https://github.com/coleifer/pysqlite3/commit/91c20016fd3fd3d1d7ade475893046958f7faa00

Berker, are you still working on this? If not, I've got a proof-of-concept version of this w/unit tests ready for review. If you'd like to have a look at it, I can create a draft PR.