PyQGIS – Adding Points with Coordinates Delimited by Commas from CSV File

csvimportpoint-creationpyqgisqgis-python-console

I can't figure out how to add point from a CSV file with the Python Console.

This is my CSV file:

UTM32_E;UTM32_N
562834,932;8762874,054
560758,523;8762624,904
562483,074;8762760,832
562131,643;8762216,202

This the code I use (I found it here : Importing CSV file to create point layer):

uri = "/Users/pugliesipc/Desktop/new.csv?delimiter=;&crs=epsg:32632&xField=UTM32_E&yField=UTM32_N"
vlayer = QgsVectorLayer(uri,'Points','delimitedtext')

QgsProject.instance().addMapLayer(vlayer)

That what I got

I know that I could rather use the graphic option of QGIS but since I have to do this with a lot of files I really would like to be able to automatise the process.

I am using QGIS 3.16.15-Hannover with Python 3.8.7 on MacOS.

Best Answer

There are several things regarding your code:

the uri for a CSV file must include the file:// prefix, as it is mentioned in the QGIS Documentation:

The provider string is structured as a URL, so the path must be prefixed with file://.
there is a method called isValid() from the QgsDataProvider class:

Returns true if this is a valid layer. It is up to individual providers to determine what constitutes a valid layer.

As was already mentioned by @BERA in his comment the reason why you do not see anything on your map canvas is because your coordinates are with , (562834,932) instead of . (562834.932).

And there are several solutions available:

A solution without changing the input CSV file

This solution based on adding the decimalPoint=',' info the uri.

#Set up inputs
absolute_path_to_csv_file = '/C:/Users/taras/Downloads/POINTS_.csv'
encoding = 'UTF-8'
delimiter = ';'
decimal = ','
crs = 'epsg:32632'
x = 'UTM32_E'
y = 'UTM32_N'

uri = f"file://{absolute_path_to_csv_file}?encoding={encoding}&delimiter={delimiter}&decimalPoint={decimal}&crs={crs}&xField={x}&yField={y}"

#Make a vector layer
layer = QgsVectorLayer(uri, "Points", "delimitedtext")

#Check if layer is valid
if not layer.isValid():
    print ("Layer not loaded")

#Add CSV data
QgsProject.instance().addMapLayer(layer)

A solution with modifying the input CSV file

There are several solutions available for replacing all commas with dots in your input CSV file:

Notepad
some Python (This solution maybe better covered on the StackOverflow)

absolute_path_to_files = 'C:/Users/taras/Downloads/'

input = open(absolute_path_to_files + 'POINTS.csv', "r")
text = ''.join([i for i in input]).replace(',','.')
output = open(absolute_path_to_files + 'POINTS_.csv', "w")
output.writelines(text)
output.close()

And then use the following code (either refer to an updated CSV file or a newly created)

#Set up inputs
absolute_path_to_csv_file = '/C:/Users/taras/Downloads/POINTS_.csv'
encoding = 'UTF-8'
delimiter = ';'
crs = 'epsg:32632'
x = 'UTM32_E'
y = 'UTM32_N'

uri = f"file://{absolute_path_to_csv_file}?encoding={encoding}&delimiter={delimiter}&crs={crs}&xField={x}&yField={y}"

#Make a vector layer
layer = QgsVectorLayer(uri, "Points", "delimitedtext")

#Check if layer is valid
if not layer.isValid():
    print ("Layer not loaded")

#Add CSV data
QgsProject.instance().addMapLayer(layer)

to get the output like this:

References:

Related Solutions

[GIS] Zooming from python console of QGIS

After getting around cookbook, the best place to learn is referring the QGis API Documentation. In this case we are looking for zoom functions, which are related to map canvas. So check if QgsMapCanvas class contains something.

enter image description here

Zoom functions available in QGis are provided in QgsMapCanvas Class.

>>> canvas = qgis.utils.iface.mapCanvas()
>>> canvas.zoomIn()
>>> canvas.zoomOut()
>>> canvas.zoomToFullExtent()

QGIS PyQGIS – Editing Bug When Adding Layers with Python Script

I can see a few potential problems with your script. Firstly, you have not passed a provider argument to your vector layer constructor. Secondly, your processAlgorithm() method is returning an empty tuple instead of a dictionary. And finally, an important piece of knowledge is that processing algorithms by default, are run in a background thread. Therefore, doing non thread-safe operations in the processAlgorithm() method (such as adding layers to the project) will often result in (at worst) crashes or at least unpredictable behaviour. To avoid this problem, it is necessary to re-implement the flags() method and return the QgsProcessingAlgorithm.FlagNoThreading flag.

The simplified algorithm below works for me and I am able to successfully edit vertices of the loaded layer.

from qgis.core import (QgsProcessingAlgorithm,
                    QgsProcessingParameterFile,
                    QgsProject,
                    QgsVectorLayer)

class CheckGcpPoints(QgsProcessingAlgorithm):

    def initAlgorithm(self, config=None):
        self.addParameter(QgsProcessingParameterFile('input_geojson', 'Properties GEOJSON', behavior=QgsProcessingParameterFile.File, extension='geojson'))

    def processAlgorithm(self, parameters, context, model_feedback):
        project = QgsProject.instance()
        property_layer = QgsVectorLayer(parameters['input_geojson'],'Properties', 'ogr')
        project.addMapLayer(property_layer)
        
        return {}

    def flags(self):
        return QgsProcessingAlgorithm.FlagNoThreading

    def name(self):
        return 'PropertyEstimates2'

    def displayName(self):
        return 'Property Estimates2'

    def group(self):
        return 'SITE scripts'

    def groupId(self):
        return 'SITE scripts'

    def createInstance(self):
        return CheckGcpPoints()

I strongly encourage you to thoroughly read the documentation about Writing new Processing algorithms as Python scripts, especially the section on Flags.

P.S. there is one other slightly confusing element to your question in that you state you are trying to load a geojson, but your script makes several references to csv. This is confusing because delimited text layers cannot be edited directly in QGIS. Therefore, I have referenced only geojson in my answer and restricted the input file extension to 'geojson'.

Further Explanation

Of course, it doesn't make much sense to write a processing script just to load a layer. If you are doing further processing, you can just define an output parameter such as a QgsProcessingParameterFeatureSink for your algorithm, and pass it to the 'OUTPUT' parameter of the processing.run() call. This way, any output layer, either temporary or file, will be handled/loaded safely, so you don't need to return the no threading flag. For example, here we run Fix Geometries on the input layer, and output the result to the feature sink.

from qgis.core import (QgsProcessingAlgorithm,
                    QgsProcessingParameterFile,
                    QgsProcessingParameterFeatureSink,
                    QgsProject,
                    QgsVectorLayer)

import processing

class CheckGcpPoints(QgsProcessingAlgorithm):

    def initAlgorithm(self, config=None):
        self.addParameter(QgsProcessingParameterFile('input_geojson', 'Properties GEOJSON', behavior=QgsProcessingParameterFile.File, extension='geojson'))
        self.addParameter(QgsProcessingParameterFeatureSink('output', 'Result layer'))

    def processAlgorithm(self, parameters, context, model_feedback):
        params = {'INPUT': parameters['input_geojson'],
                'OUTPUT': parameters['output']}
        
        fixed = processing.run("native:fixgeometries", params, context=context, feedback=model_feedback, is_child_algorithm=True)
                
        return {'RESULT': fixed['OUTPUT']}

    def name(self):
        return 'PropertyEstimates2'

    def displayName(self):
        return 'Property Estimates2'

    def group(self):
        return 'SITE scripts'

    def groupId(self):
        return 'SITE scripts'

    def createInstance(self):
        return CheckGcpPoints()