[Qgis-developer] plugins.qgis.org - Python

gordon at shieldaig.com gordon at shieldaig.com
Fri Nov 11 18:12:00 PST 2016

To answer one of my questions:


Therefore futurize (and pasteurize to backport) may be alternatives to 
2to3 and allow development of plugin code that works for both QGIS 2 and 

It would be nice to get some directions to avoid going off in the wrong 
direction or add unnecessary overhead.


On 2016-11-11 18:50, gordon at shieldaig.com wrote:
> Being somewhat unfamiliar with Python I needed to have a QGIS plugin
> to debug my code.
> I modified the QGIS remote debug code for the QGIS 2.99 development
> version.  It works on Ubuntu 16.04 and is forked from the GitHub site
> for the qgis-remote-debug plugin.
> This brought about a few questions:
> 1.  Are plugins going to be a complete break from QGIS < 2.99 in
> moving forward to Python 3.5, Qt5.7, etc?
> 2.  Is 2to3 the only way to go?  I didn't use it but it probably would
> have been easier.
> 3.  Is a plugin supposed to be backward compatible from Python 3.5+
> and Qt5.7 to Python 2.7 or less and Qt4?
> 4.  How does one code to make the plugin work in the QGIS <= 2.18 and
> QGIS >= 2.99?
> 5.  How is python-six, python3-six, or pypy-six supposed to be used or
> python-future for that matter?
> Any pointers will definitely help me produce more useful code.
> Gordon
> On 2016-11-10 18:37, gordon at shieldaig.com wrote:
>> The complication is that the plugin has to require a minimum QGIS
>> version of 2.99 but will will only show in the list if it is QGIS 3.0.
>> I have a remote debug version plugin that works on Ubuntu 16.04, QGIS
>> 2.99 dev, and Eclipse Oxygen with PyQGIS3 (Python3) environment and
>> PyDev but getting the code in-place wasn't automatic.  I manually
>> copied it over to ~/apps/share/qgis/python/plugins.  To use on Ubuntu
>> 16.04 .qgis3 (Python 3) and .qgis2 (Python 2) are hidden folders on
>> Ubuntu - so in Files-View-Show Hidden Files has to be activated before
>> the environment can be setup.
>> How is one supposed to make plugins backward compatible?  Import
>> syntax seems to be very different in Python 3 and print statement
>> syntax (among other changes) is also very different.  Can plugins pass
>> Python 2 and Python 3 lint checks or compilation?  How does one do
>> that?  The compiled python files (.pyc) are in a cache folder rather
>> in the same folder as .py files.  This is an intentional difference
>> but do they work or are they redundant?
>> Gordon
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