Updating A Plugin From QGIS 2 to QGIS 3

I have two plugins in the QGIS plugin repository, and with the release of QGIS 3 looming it was time to upgrade them for QGIS 3.

There is a short guide by the QGIS dev team that is a good starting point at:

But I had not done any development on these plugins for a while so a more step by step guide was useful, so hopefully, write the guide for the first plugin and follow it step by step for the second.

I am working on Windows, with OSGeo4W.

Before we start we will need to insure a couple of extras are installed through the OSGeo4w Installer:

Assuming GitHUB is the repo.
In git shell:

git clone

There is a conversion script for QGIS plugins provided by the QGIS devs in the main repo.

The qgis2to3 packages can be found on pip now:

We can download just the scripts folder using the following link:

Extract that into a location of your choice.

Then we can run the 2to3 script from the OSGeo4W console (cd to the folder you extracted the script to):

python 2to3 C:\path_to_plugin\QGIS_Multi_Ring_Buffer

This will print out changes that need to be made to convert from QGIS2 to QGIS3.

My first run resulted in many lines of:

RefactoringTool: Line 31: could not convert: from PyQt4.QtCore import *
RefactoringTool: Cannot handle star imports.

So my plugins line of:

from PyQt4.QtCore import *

Was impossible to convert with the tool, since I was not 100% sure what I needed from the QtCore library (I was young when I wrote the plugin). I commented out the line for the plugin in QGIS 2.8, booted up QGIS 2.8 and tried running the plugin.

So python errors:
NameError: global name ‘QVariant’ is not defined
NameError: global name ‘Qt’ is not defined
Later. I ended up expanding my other import from QtCore to:

from PyQt4.QtCore import QSettings, QTranslator, qVersion, QCoreApplication, QVariant, Qt

Running the 2to3 script again looked ok, with a number of changes required. These changes can be applied with –w flag:

python 2to3 C:\path_to_plugin\QGIS_Multi_Ring_Buffer -w

For the next step I booted up my favourite IDE PyCharm. I created a bat file that launched PyCharm with the QGIS dev environmental variables. So copying the “python-qgis-dev.bat” file from:

I changed the final line of:

"%PYTHONHOME%\python" %*


start /d "C:\Program Files\JetBrains\PyCharm Community Edition 2017.2.1\bin\" pycharm64.exe

Then from File> Settings> Project:> Project Interpreter> Set to “C:\OSGeo4W64\apps\Python36\python.exe”

It takes a while to update the interpreter.

I only had 2 errors, both for:

There is a list of API breaks between QGIS 2 and QGIS 3 at:

Looks like QgsMapLayerRegistry was moved to QgsProject. So I edit it to:


Then we can edit the metadata.txt to QGIS 3:

And increase the version number.

Then we need to recompile the icon and ui for Python3 and QT5.

I was struggling a bit with the environmental variables to get it working, and ended up using a great batch script form StackExchange:



set PATH=%PATH%;%OSGEO4W_ROOT%\apps\qgis\bin

@echo off
call "%OSGEO4W_ROOT%\bin\o4w_env.bat"
call "%OSGEO4W_ROOT%\bin\qt5_env.bat"
call "%OSGEO4W_ROOT%\bin\py3_env.bat"
@echo off
path %OSGEO4W_ROOT%\apps\qgis-dev\bin;%OSGEO4W_ROOT%\apps\grass\grass-7.2.2\lib;%OSGEO4W_ROOT%\apps\grass\grass-7.2.2\bin;%PATH%

cd /d %~dp0

::Ui Compilation
call pyuic5 multi_ring_buffer_dialog_base.ui -o          

call pyrcc5 resources.qrc -o


   echo "Failed!"


So create the .bat file and run it in the folder of you plugin (editing where needed). Note: Your resources_rc may be called resource_rc or something slightly different.

Move the plugin folder to:

Boot up QGIS2.99/3.

I had a few more issues.

It seems QGIS 3 deals with the icon slightly differently. is no longer needed, and it seems was not used on my other plugin either.

So I removed the reference to it in the main python script:
from . import icon_rc

I still had some errors.

AttributeError: module ‘qgis.PyQt.QtGui’ has no attribute ‘QDialog’

It seems QDialog has moved to PyQt.QtWidgets.

So in my file I needed to change some lines:


from qgis.PyQt.QtWidgets import QDialog, QDialogButtonBox

In the two instances in that file.

Working plugin!

Commit the changes back to the repo. Cd to the directory in git shell.

git add -A
git commit –m “Updated for QGIS 3”
git push

Zip the plugin up.
Upload to

Second plugin:
Same issue with import *
1 error with QgsMapLayerRegistry
My resources_rc file was called resource_rc so the batch script needed to be edited to:
call pyrcc5 resources.qrc -o
Same issues with QtGui.QDialog

Now time for some improvements.


UK Postcode Breakdown RegEX

UK postcodes are broken down/divided into 4 levels: Areas, Districts, Sectors, and Units.

For G12 8QH the breakdown is:
Area – G
District – G12
Sector – G12 8
Unit – G12 8QH

See my previous post:
UK Postcode Format Breakdown/

This is just a note of the RegEX strings to extract these, which can be used in QGIS, or PostgreSQL. These are a bit complex for most datasets, but should work independent on whether spaces and how many were used between the in and out codes. Should also work for London postcodes.

Area: G
RegEX: ^[a-zA-Z][a-zA-Z]?
PostgreSQL: substring(postcode, '^[a-zA-Z][a-zA-Z]?')
QGIS: regexp_substr("postcode" , '(^[a-zA-Z][a-zA-Z]?)')

UK Postcode Area UK Postcode Area

District: G12
This is actually pretty hard to do.

UK Postcode District UK Postcode District

Sector: G12 8
RegEX: ^[a-zA-Z]+\d\d?[a-zA-Z]?\s*\d+
PostgreSQL: substring(postcode, '^[a-zA-Z]+\d\d?[a-zA-Z]?\s*\d+')
QGIS: regexp_substr("postcode" , '(^[a-zA-Z]+\\d\\d?[a-zA-Z]?\\s*\\d+)')

UK Postcode Sector UK Postcode Sector

Unit: G12 8QH

I’ll let you figure this one out.

All Animations Featured OSGEO QGIS Tutorials

Storm Harvey QGIS Geometry Generator

Storm Harvey produced some extremely high levels of rainfall. Some areas of Texas received over 50 inches of rain over 9 days.

The National Oceanic and Atmospheric Administration (NOAA) provided some really great real time datasets to map the progress of the storm.

Among these were:
Hourly Precipitation
Hurricane Path

From these we can produce a GIF of hourly precipitation:

Hourly precipitation.

And total precipitation:
Hurricane Harvey Total Precipitation

Particularly the hurricane path was possible to create in QGIS using the Atlas Generator, and the excellent new:ish geometry generator. This can be found as an option for any layers symbology, as one of the renderers.

For my map I had a non spatial table that drove my atlas. This was a log table of all of the hours of precipitation I had loaded into my database. So I looped through each entry and showed the corresponding points of hourly precipitation for the corresponding hour. I also had hurricane path data as points for every 6 hours. So I could use the geometry generator to interpolate points in between known points.

While the query ended up being pretty long it is pretty straightforward.

It only needs to be run when the hour being generated does not end with a 00, 06, 12, or 18, because those are the positions I already know.

For the rest I need to generate two points. One for the previously known point, and one for the next known point.

Then I would create a line between those two points, measure the line, and place a point on the line x times one sixth of the way for the start of the line depending on the hour from the last known point.

Overall I am very impressed and happy with the result. With a bit of data defined rotation the storm progress looks great.

case when right(to_string(attribute(@atlas_feature , 'id')),2) IN ('00', '06', '12', '18') then
    get_feature(  @layer_name , 'dtg', attribute(  @atlas_feature , 'id') )
    get_feature(  @layer_name , 'dtg',  attribute(  @atlas_feature , 'id') - (attribute(  @atlas_feature , 'id') % 100 % 6  ))
    when right(to_string(attribute(@atlas_feature , 'id')),2) IN ('00', '06', '12') then
        get_feature(  @layer_name , 'dtg', attribute(  @atlas_feature , 'id') + 6 )
    when right(to_string(attribute(@atlas_feature , 'id')),2) IN ('18') then
        get_feature(  @layer_name , 'dtg', attribute(  @atlas_feature , 'id') + 100 - 18 )
    when to_int(right(to_string(attribute(@atlas_feature , 'id')),2)) > 18 then
        get_feature(  @layer_name , 'dtg',  attribute(  @atlas_feature , 'id') - ((attribute(  @atlas_feature , 'id') % 100 % 6)  ) + 100 - 18)
        get_feature(  @layer_name , 'dtg',  attribute(  @atlas_feature , 'id') - ((attribute(  @atlas_feature , 'id') % 100 % 6)  ) + 6)
case when right(to_string(attribute(@atlas_feature , 'id')),2) IN ('00', '06', '12', '18') then get_feature(  @layer_name , 'dtg', attribute(  @atlas_feature , 'id') )
else get_feature(  @layer_name , 'dtg',  attribute(  @atlas_feature , 'id') - (attribute(  @atlas_feature , 'id') % 100 % 6  ))
    when right(to_string(attribute(@atlas_feature , 'id')),2) IN ('00', '06', '12') then
        get_feature(  @layer_name , 'dtg', attribute(  @atlas_feature , 'id') + 6 )
    when right(to_string(attribute(@atlas_feature , 'id')),2) IN ('18') then
        get_feature(  @layer_name , 'dtg', attribute(  @atlas_feature , 'id') + 100 - 18 )
    when to_int(right(to_string(attribute(@atlas_feature , 'id')),2)) > 18 then
        get_feature(  @layer_name , 'dtg',  attribute(  @atlas_feature , 'id') - ((attribute(  @atlas_feature , 'id') % 100 % 6)  ) + 100 - 18)
        get_feature(  @layer_name , 'dtg',  attribute(  @atlas_feature , 'id') - ((attribute(  @atlas_feature , 'id') % 100 % 6)  ) + 6)
((attribute(  @atlas_feature , 'id') % 100 % 6) * 0.16666666666666666))

All Maps OSGEO QGIS Scotland

Every Person in Scotland on the Map

Winner of the 2016 OS OpenData Award for Excellence in the use of OpenData from the British Cartographic Society.

Full size.

The mapping process creates a random point within a building shell inside of a postcode area, which is repeated for every person in a postcode. This is in contrast to a simpler process, which does not take into account buildings at all, working simply with postcode areas. This can be seen in my previous post: Population of Scotland Mapped

Inspired by:
The Guardian – Every person in England and Wales on a map by Chris Cross

Based on the 2011 Scottish Census population data.

Data from the National Records of Scotland.

Combined with the Ordnance Survey, Open Map product.

Rendered with: QGIS tile writer python script.


Highlighting Selections in QGIS

I have been working a lot with points recently, and one thing with the default selection highlighting in QGIS is that selections do not really stand out. This is especially true with point layers.

A bit of an extreme example, but there are 15 points selected in the middle of this image.


However, we can remedy this with the Expression Plus plugin (by Nathan Woodrow) and a rule based symbology.


This plugin adds a great function: isselected()

With this we can easily create rule to symbolise features that are selected.

The rule for symbology is as follows:

QGIS 2.12+:

isselected( @layer_name )

QGIS 2.8:

isselected( 'ACTUAL_NAME_OF_LAYER' )

So we can see that 2.12 has added a slightly more dynamic way of applying the symbology.


We can now slightly more easily see our selection.


But one final setting. With symbol levels we can really make the selections pop.


Symbol levels can be set from the bottom right of the styles tab, through rendering order. We simply want out selection to have a higher number than the other symbologies. Thus being rendered in a later pass and appearing on top.


Much better.

All OSGEO QGIS Tutorials

Mapping Google Location Data

A cool python script has been created that allows you to easily convert your google location (Takeout) data into a shapefile.

You can get your data from: Google Takeout
And you only need the “Location History – JSON format”

The conversion python script can be downloaded from: GitHub

The python script requires GDAL and its python bindings, but can be easily run if you installed QGIS using the OSGeo4W installer. From the advanced installer, under the Lib section.


Then using the OSGeo4W Shell.

Run the command:

python "C:\FullPath_to_Python_Script\" "C:\FullPath_to_Input_File\LocationHistory.json" "C:\output_path" output_file_name ESRI_Shapefile


python "C:\FilePath\Takeout\Location History\" "C:\FilePath\Takeout\Location History\LocationHistory.json" "C:\FilePath\Takeout\Location History" output ESRI_Shapefile

Then just style it in QGIS as desired.

All OSGEO QGIS Tutorials

GIS to CAD using ogr2ogr – Part 2 – GML to DXF with OS MasterMap

GIS to CAD using ogr2ogr – Part 1 – Shp to DXF with Contour Data
GIS to CAD using ogr2ogr – Part 3 – Point Annotation to Text in CAD

For this example we are using Ordnance Survey MasterMap Topology Layer data.

MasterMap Topo Sample Data:

Now we know that we can maintain an attribute through layers, as we saw in the shp to DXF example, the export of MasterMap should be straightforward.

Let’s first see what the GML file contains.

ogrinfo -so os-mastermap-topography-layer-sample-data.gml
Had to open data source read-only.
INFO: Open of 'os-mastermap-topography-layer-sample-data.gml'
using driver 'GML' successful.
1: TopographicArea (Polygon)
2: CartographicText (Point)
3: CartographicSymbol (Point)
4: BoundaryLine (Line String)
5: TopographicPoint (Point)
6: TopographicLine (Line String)

So we have 6 layers in total.

For MasterMap in CAD we will be mainly interested in CartographicText, TopographicPoint, and TopographicLine.

Lets start with TopographicLine.

ogrinfo -so os-mastermap-topography-layer-sample-data.gml TopographicLine

Nothing too useful.

A bit more details:

ogrinfo os-mastermap-topography-layer-sample-data.gml TopographicLine


fid (String) = osgb1000000347615024
featureCode (Integer) = 10019
version (Integer) = 5
versionDate (String) = 2005-03-30
theme (StringList) = (2:Buildings,Land)
accuracyOfPosition (String) = 1.0m
changeDate (StringList) = (4:1994-01-26,2003-11-10,2004-02-19,2005-01-05)
reasonForChange (StringList) = (4:Modified,Attributes,Attributes,Attributes)
descriptiveGroup (String) = Building
physicalLevel (Integer) = 50
physicalPresence (String) = Obstructing
descriptiveTerm (String) = Outline
make (String) = Manmade
nonBoundingLine (String) = (null)

For this feature the “descriptiveGroup”” seems the most useful, and from reading the os-mastermap-topography-layer-user-guide.pdf the best would be either a combination of descriptiveGroup and descriptiveTerm or using the featureCode. Since this is a simple conversion we will just use a combo of descriptiveGroup and descriptiveTerm to create our DXF layers.

I will be using || for concatenation, which works with the SQlite SQL dialect.

ogr2ogr -f DXF TopographicLine.dxf os-mastermap-topography-layer-sample-data.gml TopographicLine -sql "select descriptiveGroup || ' - ' || descriptiveTerm as Layer from TopographicLine" -dialect SQlite


layer names ignored in combination with -sql.
ERROR 1: No known way to write feature with geometry 'None'.
ERROR 1: Unable to write feature 0 from layer SELECT.

ERROR 1: Terminating translation prematurely after failed
translation from sql statement.

Not quite. Seems to be missing geometry, perhaps a SQL select issue.

This can be tested with:

ogrinfo os-mastermap-topography-layer-sample-data.gml TopographicLine -sql "select descriptiveGroup || ' - ' || descriptiveTerm as Layer from TopographicLine" -dialect SQLITE


Layer (String) = Building - Outline

Layer (String) = Building - Outline

So we do not have any geometry. Lets bring that in.

ogr2ogr -f DXF TopographicLine.dxf os-mastermap-topography-layer-sample-data.gml TopographicLine -sql "select descriptiveGroup || ' - ' || descriptiveTerm as Layer, * from TopographicLine" -dialect SQLITE

Geometry looks good:


But if we check the attributes in QGIS:


We can see that all of the attributes that are not 0 have both a descriptiveGroup and a descriptiveTerm, which was not what we can see in the ogrinfo summary. So our SQL statement is cutting some out.

Try again:

ogr2ogr -f DXF TopographicLine2.dxf os-mastermap-topography-layer-sample-data.gml TopographicLine -sql "select descriptiveGroup ||' - '|| coalesce(descriptiveTerm,'') as Layer, * from TopographicLine" -dialect SQLITE

Looking better:


But it won’t open in AutoCAD DWG TrueView. Lets try running it through a ShapeFile format first before the DXF conversion.

ogr2ogr TopographicLine.shp os-mastermap-topography-layer-sample-data.gml TopographicLine -sql "select descriptiveGroup || ' - ' || coalesce(descriptiveTerm,'') as Layer, * from TopographicLine" -dialect SQLITE

ogr2ogr -f DXF TopographicLine3.dxf TopographicLine.shp



No indication of why a direct GML to DXF conversion would hang TrueView, and your mileage with other CAD software may vary. But ShapeFile is a very simplified geometry format, so perhaps running through that helps with some more complex geometry in the GML. Hard to say with no errors from TrueView, just a stuck program.

Repeat for point:

ogr2ogr -f DXF TopographicPoint.dxf TopographicPoint.shp

ogr2ogr TopographicPoint.shp os-mastermap-topography-layer-sample-data.gml TopographicPoint -sql "select descriptiveGroup || ' - ' || coalesce(descriptiveTerm,'') as Layer, * from TopographicPoint" -dialect SQLITE

GIS to CAD using ogr2ogr – Part 1 – Shp to DXF with Contour Data
GIS to CAD using ogr2ogr – Part 3 – Point Annotation to Text in CAD

All OSGEO QGIS Tutorials

GIS to CAD using ogr2ogr – Part 1 – Shp to DXF with Contour Data

GIS to CAD using ogr2ogr – Part 2 – GML to DXF with OS MasterMap
GIS to CAD using ogr2ogr – Part 3 – Point Annotation to Text in CAD

The power of GDAL, and specifically ogr2ogr is pretty impressive. This conversion is from shp to DXF, which is a somewhat universal CAD format so further conversion should be possible.

This post will cover contour export while maintaining 3D elevation, in addition to contour values as layers in CAD. The data used is OS terrain 50.

OS Terrain 50:



Contours in 3D:

ogr2ogr -f DXF contour_zfield.dxf SX99SW_line.shp -zfield PROP_VALUE

With the -zfield creating the 3d elevation.

Great result:


The alternative is to just store the z-value as layers.

ogr2ogr -f DXF contour_layer.dxf SX99SW_line.shp -sql "SELECT PROP_VALUE AS Layer FROM SX99SW_line"

Layers work great:


With the ogr2ogr DXF driver, if you have an input column called “Layer” then it will be used to group features as a layer in DXF. We use a SQL query to achive this. Prop_Value is the height field in my input data.

And putting them all together:

ogr2ogr -f DXF contour_zfield_layer.dxf SX99SW_line.shp -zfield PROP_VALUE -sql "SELECT PROP_VALUE AS Layer FROM SX99SW_line"

Result not as expected, flat output:


Adding our SQL select statement removes our zfield attribute as such ogr2ogr cannot access it. Lets resolve this:

ogr2ogr -f DXF contour_zfield_2_layer.dxf SX99SW_line.shp -zfield PROP_VALUE -sql "SELECT PROP_VALUE AS Layer, * FROM SX99SW_line"



Layers and height.

GIS to CAD using ogr2ogr – Part 2 – GML to DXF with OS MasterMap
GIS to CAD using ogr2ogr – Part 3 – Point Annotation to Text in CAD

All OSGEO PostGIS QGIS Scotland

Multi Ring Buffer – Buffer the Buffer or Incrementally Increasing Distance?

Does it matter, and who cares?

Multi-ring buffers can be useful for simple distance calculations as seen in:
X Percent of the Population of Scotland Lives Within Y Miles of Glasgow
X Percent of the Population of Scotland Lives Within Y Miles of Edinburgh

For these I simply created multiple buffers using the QGIS buffer tool. This works for small samples, but was quite frustrating. I had initially hoped to do the whole analysis in SQLite, which worked pretty well initally, but struggled on the larger buffers. It took too long to run the queries, and did not allow for visualisation. I think using PostGIS would however be pretty feasible.

But creating a multi-ring buffer plugin for QGIS also seemed like a good learning experience. Which got me thinking, does it matter if you create increasingly large buffers around the original feature, or if you buffered the resulting buffer sequentially. My hypothesis was that there would be pretty significant differences due to the rounding of corners.

I asked on StackExchange but the conversation did not really take off:

My question is not about the overlapping-ness of the buffers, since I think multi-ring buffers should be “doughnuts” anyway. But rather if smoothing will occur. The only answer was to try it myself.

Buffer styles:
Buffer the resulting buffer sequentially: Sequential
Buffer the original feature with increasing buffer distance: Central
[table caption=”Speed – In seconds”]
Features, Rings,Central, Sequential
1, 5, 0.59, 0.56
55, 5, 8.06, 6.38
1, 200, 60.83, 31.76
3, 200, 62.89, 40.89
55, 200, 628.38, 586.67
1, 2000, 203.84, 67.00

No matter how you do it the sequential style is quicker, but that may be down to my code.


Interestingly, although understandably, the sequential style results in a lot more vertices in the outer rings. For comparison, for a 500 ring buffer the outermost ring had the following vertice counts:
Style, Vertices

We can see this with editing turned on.

We can also see a smoother profile in the sequential buffer. However the difference is not major, and hard to discern with the naked eye.

So we have at most about around a 10m discrepancy, with 500 50m rings, so around 25000m of distance from the original feature.
This impacts rendering time dramatically, an example with our 500 rings:



So quicker to create but slower to draw. So which one is better, quicker calculation, or quicker rendering? Or should we not do 200+ ring buffers?

Hard to say. In version 0.2 of the Multi Ring Buffer Plugin. There is an option for either in the advanced tab.

Please report any issues through GitHub:

All Mapvember OSGEO PostGIS QGIS Scotland

Mapvember 2014

Mapvember: A map/tutorial a day for every day in November.

Some days had more than one map, some had tutorials, one just had a photo. Some were very easy, others would have take a couple of days of work.

Excellent experience, good learning experience and an opportunity to post previous projects that were a bit short of being great. A little time consuming at times though. I started making the maps around half way through October, so I had almost the first week ready when November began, but the days ticked by quickly. Happy to have done it. I encourage everyone to join in next year, or any other month.

Visitor Statistics:

Total views: 3047
Uniques: 2289
Pageviews: 4327

Top 10 Countries:
United Kingdom: 1147
United States: 363
Germany: 183
France: 120
Canada: 85
Italy: 67
Spain: 66
Australia: 56
Switzerland: 42
India: 39

Mapvember Countries

Top 10 Cities:

Glasgow: 340
London: 212
Edinburgh: 122
Rostock: 45
Aberdeen: 42
Stirling: 35
San Jose: 31
Vienna: 28
Berlin: 28
Zagreb: 26

Mapvember Cities

Other Months:
August Visitors: 303
September Visitors: 641
October Visitors: 523
November Visitors: 3047

Most popular posts:
X Percent of the Population of Scotland Lives Within Y Miles of Glasgow – 521
Glasgow Subcrawl Map – 400
Polygon Outlines in QGIS – 276
Setting up PostgreSQL and PostGIS on Linux Mint (Not posted in November) – 258
Glasgow 3D Residential Property Density QGIS2threejs – 218
Georeferencing Vector Data Using QGIS and ogr2ogr (Not posted in November) – 173
Great Circle Flight Lines in Postgis – 171
London Bus Route Maps – 154
Centroid Within Selection in QGIS – 114
QGIS Inverse Shapeburst Fills – 109

Referrals: 747 381
Twitter: 122 71
Facebook: 70
Flickr: 15

Top SubReddits:

/r/glasgow: 200
/r/scotland: 120
/r/london: 46
/r/gis: 19
/r/QGIS: 4

Thanks for visiting.