Python bindings for QGIS.

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Using pyqgis with existing ArcGIS files

I'm pretty new to GIS. I have some files that seem to have been created using ArcGIS (I got them from here http://www.fao.org/ag/againfo/resources/en/glw/GLW_dens.html). I would like to do some ...
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30 views

QGIS plugin, extending plugin stub, instance has no attribute error

Update This is not an answer to why it does not work when the method is defined inside the class, but a workaround. Simply defining the method outside, prior to, the class (something that Evil ...
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1answer
97 views

Got Null values when updating attributes with PyQgis

I'm trying to create and update a field and ,for now, just change it's value to 2. Here is my code: layer = qgis.utils.iface.activeLayer() index = layer.fieldNameIndex("P") # if index == -1: # ...
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1answer
231 views

How to merge shape files with attributes from a python script in QGIS?

I have some shape files. They are all the same kind of shape and all have the same attributes. If I wanted to merge them manually the "Vector/Data management tools/merge shape files to one" works ...
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1answer
257 views

AttributeError: 'module' object has no attribute 'Open'

Hy, I am running the following code which I found on: GDAL - Perform Simple Least Cost Path Analysis which I adapted to my case, but I get the following error when running the code in the python ...
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1answer
110 views

Failed load delimited layer in QGIS python console

I'm trying to follow the map rendering section from the pyqgis cookbook. I am able render shape file using qgs vector layer, however getting error prompt while loading delimited text file through qgs ...
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55 views

using postgis function in pyqgis

I'd use Postgis function in Pyqgis script. This code: qsql="(select gid, id, St_Buffer(the_geom,200) as geom from archi)" uri = QgsDataSourceURI() uri.setConnection("ip", "port", "x", "x", "x") ...
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1answer
170 views

Code works on python console in QGIS but same doesn't work in stand alone script

I'm trying map rendering with stand alone script, so I have small script which works fine in python console provided QGIS, however when I run same code in stand-alone script it executes without error, ...
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1answer
42 views

Rendering PyQGIS objects in MapCanvas

I'm quite new to PyQGIS and have what is probably a pretty basic question, but I haven't been able to pick it up from the documentation. I have a QgsVectorLayer object from a PostGIS server, and I ...
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28 views

Display errors with QGIS Python Console

I'm using qgis 2.0.1 and I'm just starting to try to use the python console. From what I can tell the functionality of the console is fine (I'm not getting any unexpected errors) but when I'm typing ...
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1answer
148 views

Load and display a layer using PYQGIS

I'm having a go at using pyqgis from within the QGIS python console to load a layer from SQL Server and display it. I feel like I'm part way there but I'm having a real issue getting the layer to ...
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1answer
87 views

How to call a method by BOTH a button AND a key shortcut

I have been trying to call a method by BOTH a key shortcut (as described here http://www.qgis.org/en/docs/pyqgis_developer_cookbook/snippets.html) and a button I created on the toolbar. The button ...
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21 views

What's the conversion coefficient between millimeters and QSize units in Qgis?

What is the conversion coefficient between millimeters and QSize units in Qgis ? What i have in mind is to set the paper size (via setPaperSize()), knowing the size of the composed image. That is why ...
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1answer
25 views

how to compile qgis-1.8.0 on ubuntu

i have downloaded qgis-1.8.0.tar.bz2 and I want to install it on my linux computer(12.04 LTS). How can I perform it please? I do it because I am desperate with Qgis 2.0.1 Dufour on ubuntu 12.04, ...
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1answer
57 views

How to change the default gray color of the QgsComposition background?

I'm building a map, with elements like QgsComposerMap of course, but also QgsComposerLabel, QgsComposerLegend ,etc... Each of these elements has a boolean "setBackgroundEnabled" property, to make them ...
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4answers
103 views

Why QgsMapCanvas only appear after lost focus?

I created the simple frame .UI file, compiled with pyuic4, and tried the ShapeViewer.py to load the shapefile "world_borders.shp". However, the map doesn't display at the first time. I have to click ...
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16 views

random point through raster

I've some issue in some task pls help if you can as I've not good python skills. I've a raster with values from 5 to 97 and I want a python script which can scan the raster and generate random points ...
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68 views

Add memory layer to a preexisting PostGIS table

I'm trying to append a memory layer to a preexisting PostGIS table. The DB connection is already established (in this way: How to properly establish a PostgreSQL connection using QgsCredentials) and, ...
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74 views

How to fetch openlayers layers from pyqgis?

My objective is to fetch maps provided by openLayers, as in openLayers_plugin, from a stand alone python script. I would like to get it superposed to my shp file. As can be read on ...
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42 views

How to get the signal when the color changes in pyQGIS?

I would like to have the signal when the color of a vector layer is changed by the user. In the doc, there is a signal that seems to fit ...
2
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1answer
107 views

How to write a new layer to PostgreSQL from QGIS plugin

The PyQGIS cookbook states that QgsVectorFileWriter can write vector layers to any format supported by OGR: https://www.qgis.org/en/docs/pyqgis_developer_cookbook/vector.html#writing-vector-layers ...
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42 views

How to add field to postgres layer with PyQgis?

I'm fetching a posgtres layer with PyQgis and then I'm trying to add field with this: lyr.startEditing() lyr.addAttribute(QgsField("class", QVariant.Int)) But It is not adding the field and also ...
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38 views

Add feature to csv via PyQGIS

I'm using PyQgis 2.0.1. Is it possible to add feature to csv file? I've tried to do this as it's shown in CoockBook: if caps & QgsVectorDataProvider.AddFeatures: feat = QgsFeature() ...
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2answers
56 views

How to programmatically fill a datetime field with datetime.datetime.now() function

I have been trying to programmatically fill a datetime field using values coming from datetime.datetime.now() function. #I create the temp shp using a URI URI = ...
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53 views

How to apply categorized symbols to polygon layer with PyQgis?

I'm fetching a polygon layer from postgres like this: uri = QgsDataSourceURI() uri.setConnection("localhost", "5432", "mydb", "postgres", "xxx") uri.setDataSource("public", "my_table", "geom") lyr = ...
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65 views

Install PyQGIS in virtualenv

Is it possible to install PyQGIS in virtual environment? I want to use rendering capabilities in my own application which runs using virtualenv.
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97 views

PyQGIS + PostGis: FATAL: sorry, too many clients already

I searched for questions regarding this problem and hadn't find one. I'm developing a custom application with a map canvas to show some geographic information from a PostGis database. After some ...
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1answer
61 views

How to properly establish a PostgreSQL connection using QgsCredentials

I'm trying to establish a Postgres connection using QgsCredentials as described here: How to access user credentials in database connection? The only problem is that I cannot establish a working ...
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1answer
117 views

How can I modify layer order with the QGIS python API

Typically, after a new_layer = addRasterLayer(...) that inserts new_layer before the active layer, I'd like to move it to the top of the table of contents. How to do it? I use an existing QGIS ...
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39 views

How to get the color of a vector layer in pyQGIS?

I have see this topic (How to change the color of a vector layer in pyQGIS?) but I'm looking for get the color not to change. How I can resolve my problem ? Thanks
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1answer
99 views

QGIS python - identify and highlight features programatically

In QGIS there is an option to select features of a selected layer using a "identify feature" tool. Then the feature get highlighted in a different color and attribute dialog is poping up. like that i ...
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85 views

How to programmatically set a rule-based renderer in QGIS?

These days im in a process of developing a plugin , which highlights/change color of set of features in a vector layer depending on some calculation. i found nice article about QGIS – Rule based ...
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2answers
131 views

How to get the file paths of the loaded layers in a QGIS plugin?

I am very new to GIS, QGIS and Python so please bear with me. I am using QGIS 2.0 and I would like to develop a QGIS plugin that would display the raster layers of the main window in order to allow ...
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2answers
466 views

How to perform SQL queries and get results from QGIS python console?

I'm writing a python script using QGIS API. I have to get results from postgres database table. The table has geometry field and other non-geometry fields. I want to perform SQL queries on ...
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1answer
115 views

How to find the polygons bordering a feature programmatically with qgis?

Is there a way to calculate the neighbors of a polygon with pyqgis for every feature? For example, the selected polygons relative to the one in the center: I found this solution, but it's a year ...
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76 views

How can i add a north arrow in QgsComposition?

I'm trying to add an svg image of north arrow in QgsComposition using this code: mapRenderer = iface.mapCanvas().mapRenderer() theComposition = QgsComposition(mapRenderer) ...
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1answer
46 views

Halt QGIS on startup

I have a custom made login form in Python, which launches on QGIS startup. But before the user has a chance to enter the credentials, the program starts normally, bypassing the form. From then on the ...
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1answer
271 views

Writing Stand Alone PyQGIS Script - QGIS 2.0

I have spent quite a bit of time looking for a clear answer this topic and have still been unable to really accomplish my goal of accessing PyQGIS in a stand alone script. Parts of answers have been ...
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1answer
81 views

How can I add grid lines to a print composition using pyqgis?

I'm writing a qgis plugin to create an image in the print composer of the current map. I can get the map rendered in the proper place with a frame of the right width, and I can get grid annotations ...
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1answer
43 views

How to add a vector layer in QGIS in python

Someone please can help me how to start with the library qgis ? At first, i'd like to know, by clicking in a button on my litle plugin that i created for QGIS how to add a vector layer with python ...
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1answer
33 views

How to randomly select from existing points within each polygon?

I have a polygon layer (where each feature has a class attribute), and a point layer, and there are at least 10 points within each feature of the polygon. Is there a way to randomly select only "k" ...
1
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1answer
45 views

PyQGIS 2.0 API problem reading attributes

Im reading some attributes from shapefile features in a loop. According to this: http://nathanw.net/2013/06/13/new-qgis-20-api/ I should be able to reference my attributes (and getting native python ...
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1answer
312 views

QGis 2.0.1 mapserver extension missing

I tried to export my Qgis projects to mapserver, using RT mapserver extension, because there is not any other extension in my version of QGis.(QGis 2.0.1 Dufour on ubuntu 12.04 LTS). After installing ...
3
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2answers
320 views

Rendering and Labeling Shapefile with PyQGIS

I've been running into a few problems working with the QGIS API for python. I've gotten more comfortable working in the python console in QGIS but I run into problems when I try to run the code ...
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0answers
20 views

MSHP file from SAGA tough to delete

After running a SAGA line dissolve process in QGIS, an MSHP file is created (amongst other things). Fine by me, though I'm not sure what it's used for (metadata in XML format?). Problem is that it ...
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2answers
221 views

Using Python and open source modules, how can I perform Raster Calculator functions?

I would like to perform mathematical functions similar to those you would use Raster Calculator for in ArcMap, however I'd like to do it in Python without using the Arcpy module. I have the osgeo ...
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1answer
129 views

QGIS 2.0 Plugin: Select and Identify a Single Feature

given is a layer with some nodes on it and every node has some attributes(name, id, etc...). For showing up the informations of a single node I can use the "Identify Feature Tool". Choose the tool, ...
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285 views

On install “Couldn't load SIP module.” - should I reroute Python config or download sip?

(Please note I'm still relatively new to Linux). When I run QGIS after install I get a message 'Could't load SIP module'. I've looked for help and am conflicting advice on what my next step should ...
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1answer
90 views

How to programmatically add an algorithm from external plugin to QGIS processing toolbox?

I'm writing a python plugin for QGIS and I'd like to know if it's possible to provide an interface to it from the processing toolbox. I can see how the existing algorithms are loaded into processing ...
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68 views

Missing pyexpat on QGIS 2.0.1: pyuic4 fails

I have encountered a problem when trying to develop a custom plugin for QGIS 2.0.1 (Python 2.7.5 with two additional Python installations on the same machine). When I try to compile the UI file ...