Python bindings for QGIS.

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30 views

Can't get my QGIS external map to display on Ubuntu trusty: QObject::connect: Cannot connect (null) error

I've been following along the examples from the book "Building Mapping Applications with QGIS and for the life of me I can't figure out why my shape files aren't loading and displaying in the app ...
2
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1answer
42 views

How to load a style from POSTGIS in PyQt

The thing is that I have four styles I have created in QGIS through the GUI and saved into a postgresql database. I can see them in the table named layer_styles I have seen similar questions asking ...
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2answers
40 views

How can I create a QGIS plugin that needs an external Python library?

I’m trying to enhance QGIS's Profiletool plugin by adding DXF export functionnality. For this, I need to to import dxfwrite library. As it's installed on my computer, i added the following lines to ...
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0answers
45 views

How to access a deleted features attributes (before committing)

I have a signal setup for a feature deletion event on a layer: self.layer.featureDeleted.connect(self.feature_deleted) When I try and grab an attribute from the deleted feature on the slot, a ...
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1answer
34 views

My QGIS plugin shows GUI but not Works. How to get Error log?

I am new to PyQgis. I made a simple calculator with PyQt4, now I am trying to run it under QGIS. I connected calculator as plugin, and tested it, its GUI works without error but it does not calculates ...
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10 views

Launch processing tool user interface using python command

I am trying to launch the user interface of a processing algorithm using Python script but I cannot find a simple way for it (aside double clicking on it in the process toolbox of course). The plugin ...
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1answer
70 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 ...
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2answers
48 views

Polygons in one layer have different attributes

Is it possible in PyQGIS to have in one layer more polygons and some would have one set of attributes and another different? E.g. Polygon_1(name, size, average_age), Polygon_2(name, size, ...
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577 views

How to delete selected features in Qgis using Python

I have a shape file with only one field DN. I would like to delete all features which does not have specific value of the field. Let say the DN can be 1,2 or 3. So far I was able to find out how to ...
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15 views

What solutions to use QGIS as insert tool for a Postgres relationnal database?

I have a Postgres/PostGIS relational database and I would like to use QGIS as an interface for inserting data. The thing is that my database is quite complex and I need my tool to handle the following ...
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2answers
228 views

How to create a polygon feature using Python?

I'm making a plugin for Quantum GIS in python. I have a polygon layer and want to create a new feature. So far, I have this because I need a polygon geometry to add the feature: surface = ...
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1answer
34 views

How to find if map layer registry is empty?

In my script I want to open layer named my_layer if it is in the map layer registry. I use following code for it: inputLayer = QgsMapLayerRegistry.instance().mapLayersByName("my_layer")[0] If not ...
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1answer
927 views

QGIS python - reference a layer in the table of contents

I'm trying to create a plugin for QGIS using python, But need some help. I want to 1.Zoom to a layer and 2. make the layer visible(switch off or on). But I have managed to zoom to an active layer by ...
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1answer
354 views

How to begin with tool development for GRASS gis or QGIS GRASS

I wanted to begin with customized tool development in Grass GIS or QGIS grass. How should i begin in to develop the tool. I search a lot in google search engine for begin with tool development in ...
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2answers
22 views

How to put a frame around a legend using QgsComposerLegend?

I can already see this being a simple answer but I'm stumped with this. I want to create a frame around a legend created by a PyQGIS script Code snippet is: legend = QgsComposerLegend(c) ...
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2answers
3k views

How to access attribute data type in QGIS?

I've been developing a plugin on QGIS platform using PyQGIS. So far plugin does the following: You can select any feature of the already loaded vector layer in QGIS. After selection, plugin displays ...
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1answer
25 views

QGIS: Finding electric network loops

With QGIS, how can we analyse an electrical network to find loops? Using Python is not a problem, however there is not a solution in the QGIS Python API. The QgsGraphAnalyzer has dijkstra and ...
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35 views

How to rename field names in a shapefile attribute table without table manager using python

By using the table manager we can rename the field names but i want to rename of fields using python. How can i do that?
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1answer
16 views

How to read non-spatial data using PyQgis?

I'm generating maps with QGis. What I do is generate a bunch of non-spatial data on a set of cities (using VBA), and still using VBA, generate a python code that will automaticaly output general map ...
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2answers
48 views

How to create a polygon grid with un-even spacing between research plots?

I have an orthomosaic of a crop field with small research plots (3.8 X 1.44 m and 0.22m b/w plots and 0.50m b/w range spacing). I would like to create a polygon layer using this information. After ...
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1answer
41 views

How to place labels at the boundary of the current map extent

I have a layer of reference grid lines on top of several map layers. The grid lines should be labeled with coordinate values: vertical grid lines with x-values and horizontal lines with y-values. The ...
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9 views

Iteratively Change Object's Instance Attributes PyQGIS

I am trying to create new instance attributes (NOT feature attributes) for a collection of features in a vector layer in PyQGIS. I'm getting some weird results and am wondering if this is even ...
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2answers
53 views

How to join the attributes table from one input layer to another layer with unique id using python

I have one input layer with the attibute values and i wanted to join the attribute table of the input layer to the another layer with unique values using python. ...
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9 views

dynamic styles for rasters in qgis processing

I am writing a qgis processing script that loops a table column and does interpolation and would like to know if it is it possible to generate styles on the fly for raster layers and how to do it. I ...
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0answers
24 views

Using Multiprocessing inside a plugin in Qgis

I spent quite a bit of time looking on how to use the multiprocessing package, but couldn't find anything on how to use it inside a plugin in QGIS. I am developing a plugin that does some ...
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1answer
265 views

How to copy the color styling to a color column in a layer's attribute table?

I have a polygon layer in QGIS that I have applied a random color style to each polygon. Under Layer Properties -> Style I selected a Categorized style and then generated a random color ramp. I added ...
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1answer
18 views

Checking for Changes in a WFS

I'm responsible for updating many spatial datasets within my organisation. Some data suppliers notify me of a change, some suppliers don't. Sometimes it's not easily apparent if the data has changed ...
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1answer
40 views

Refreshing “layer render order” widget

i made changes in the render order of my map canvas using a : qgis.utils.iface.mapCanvas().setLayerSet(a) "a" being a list of QgsMapCanvasLayer My code is working as expected (i see result on map ...
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1answer
149 views

How to print 2 maps in the same PDF page using PyQGIS?

I am trying to generate a one-page PDF document containing the following items: 1) On the left half, a full state map (say, New York State). 2) On the top right quadrant, a map that zooms in to one ...
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1answer
50 views

QStringList() error in plugin of QGIS 2.10

I have made a Dialog in PyQt for use it like a plugin under QGIS 2.10 The Dialog works fine like a standalone application, but if I try to call it like a QGIS plugin, I get this error: ...
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1answer
22 views

Failed to create memory layers in QGIS application on Linux

I have written a python class which reads properties of map layers from an XML file and creates appropriate memory layers. I have developed and tested this code with QGIS 2.8.2 on a Windows 7 machine ...
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1answer
25 views

How to dynamically change images in map reports?

I need to make a report about several cadastral parcels which data are contained inside three different tables of a database. Report must contain: Cadastral data taken from the three tables A ...
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2answers
32 views

Where is the QGIS API action for “deselect”?

Where is the QGIS action for the “deselect” toolbutton in the 'Attributes" toolbar? I do not see this action in the QgisInterface class or do not recognize it by name. Is it missing from iface? I'd ...
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18 views

How to write a test suite for QGIS standalone application

I have a rather simple QGIS standalone Python app (2.8.2, Windows 7/64), with some published methods to create different types of geometric primitives (rectangles, circles). class MyApp(QMainWindow, ...
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1answer
38 views

How to calculate zonal statistics from multi-band raster for each polygon using python?

I want to calculate the zonal statastics from multi band raster for a polygon layer. When I am using this snippet of code: vectorlayer=qgis.utils.iface.mapCanvas().layer(0) rasterfile = ...
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2answers
314 views

How to determine the coordinates of the corners of the raster layer

How can we determine the coordinates of the corners of the raster layer? The image opens function QgsRasterLayer.
2
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1answer
61 views

How to avoid a QGIS crash when it is appended a symbol layer in a symbol?

When I run the next code at the Python Console of QGIS with a line vector layer: symbol1 = QgsLineSymbolV2.createSimple({'penstyle':'solid', 'color':'black', ...
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1answer
53 views

Processing algorithm fails from Python script

I'm trying to write a Python script performing a geoalgorithm. What is surprising me is the following: I first test the algorithm by QGIS (2.8) interface. In my case, the GRASS interpolator ...
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0answers
19 views

PyQGIS Use of predefined color ramps

I´m trying to apply one of predefined color ramps to a categorized field in a vector layer. To do this, I'm using the code below suggested by Irssvt in another post. However, I cant´t see the result ...
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1answer
25 views

Styles not applied when using QgsMapRenderer

Using pyqgis, i am trying to export some maps as images using QgsMapRenderer. Here is the layer/style setup, both load correctly: lyr = QgsVectorLayer(uri.uri(), 'Report', 'postgres') styleload = ...
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2answers
147 views

How to read Oracle data with PyQGIS? (“identifier is not long” error)

Do you have any idea how load Oracle spatial data to QGIS with using the PyQGIS? Is it possible? I try: uri = QgsDataSourceURI() uri.setConnection("*host*", "1521", "*database*", "*username*", ...
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0answers
59 views

How to wait for mapCanvas render before taking a screenshot?

i am trying to iterate over a large list of features and making a screenshot of the selected feature. My problem is that it seems to be a delay between the refreshing of the canvas and the taking of ...
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0answers
23 views

How to react to network events

I am in the process of writing a Plugin which should react to some data (XML-Format) sent via a socket connection. Since I have never worked with IPC in terms of python before and my knowledge of IPC ...
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1answer
40 views

How to get the coordinates inside the polygon using python

I have a polygon and using this code snippet we can get the coordinates boundary of the polygon. canvas = qgis.utils.iface.mapCanvas() aLayer = canvas.currentLayer() coord = ...
2
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1answer
27 views

Show VectorLayer in window

I'm new in PyQgis. I can create vector layer and lines/polygons on it : layer = QgsVectorLayer("LineString", "points", "memory") pr = layer.dataProvider() pt = QgsFeature() point1 = QgsPoint(0,0) ...
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2answers
246 views

Is there a function to select a region of a map for further processing with Python?

I would like to select a map's region in QGIS for further processing with python console. Ideally I would like to select the region with a mouse drag (like Gimp crop function) and then e.g. analyze ...
3
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1answer
40 views

Moving cursor using PyQGIS?

I would like to move the cursor to a given x,y coordinates of the MapCanvas. Is there an easy way to do this using PyQGIS?
3
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1answer
1k views

legend groups and layer position/order qgis 1.8

I'm tring to programmatically create layer sequence also using groups. Simple python code: layer = QgsVectorLayer("004cp000.shp", "004cp000", "ogr") QgsMapLayerRegistry.instance().addMapLayer(layer) ...
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1answer
230 views

Adding new menu item to QGIS Desktop app

I need to add new menu item to the top level menu of QGIS Desktop (2.7.0); I.e. it shall be on same level as "Project", "Edit", "View", "Layer" etc. As far as I know there is pretty nice way how hide ...
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1answer
152 views

How to enable the snapping options for vector layer using the python programming?

I want to enable the snapping options for the the existing layers using python programming. How can I do this?