[Qgis-developer] Qt5 and Python 3

[Matthias Kuhn]

Hi,

I have just published a post with the state of Python 3 and Qt 5 migration.
http://www.opengis.ch/2016/05/04/qgis-qt5-and-python3-migration-current-state/

In general I am very happy with what we have achieved so far.

There is one problem that I think needs broader discussion which is an
issue about the handling of NULL values in PyQt5. With the equivalent to
the SIP API V2 we don't have PyQtNullVariant up to PyQt 5.6. This
basically means, no NULL for python plugins. And I consider this a blocker.

We could

 * Switch to another API (sip.enableautoconversion(false), similar to
SIP API V1). Resulting in countless lines of code in plugins requiring
to be updated.
 * Bump the minimum Qt version to 5.7 (and hope that PyQtNullVariant
will be fixed there, chances are good, see
https://www.riverbankcomputing.com/pipermail/pyqt/2016-April/037336.html).

I tend towards Qt >= 5.7 - on Windows and Mac we control the
dependencies, so that should be ok anyway, on Linux we can say "if you
want a recent QGIS, get a recent distro". And by the time we actually
ship QGIS with a Qt5 dependency there should be a number of distros with
Qt 5.7.

Any opinion on this?
Matthias