QGIS – How to Efficiently Reproject 500 CSV Files Using PyQGIS

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I know, my question is similar to some old ones on this site.

I've a lot of CSV files (geo coordinates) to import to qgis (and then to convert them), and the usual way is not the best way to do it (too long).

I have almost 500 CSV files (wgs84 coordinates) and this is what I want to do:

  1. Import all CSV files at once into QGIS
  2. Project them
  3. Export them into CSV files (again) but with different coordinates (convertion to UTM33N)

I'm trying to understand how to use the python console but I'm not moving on 🙁

Can anyone explain to me how to achieve it step by step?

Best Answer

If you're looking to reproject csv files from the Python Console in QGIS then you could use the following script. All you would need to change are the three paths which are mentioned in the comments.

Essentially, the script imports your csv files into QGIS as shapefiles (assuming your geometric fields are named X and Y). It then uses the qgis:reprojectlayer and qgis:fieldcalculator algorithms from the Processing Toolbox to reproject and update the X and Y fields with the new coordinates. It then saves these in a folder and converts them to csv files in a path you specify. So in the end, you have updated shapefiles and csv files in separate folders.

import glob, os, processing

path_to_csv = "C:/Users/You/Desktop/Testing//"  # Change path to the directory of your csv files
shape_result = "C:/Users/You/Desktop/Testing/Shapefile results//"  # Change path to where you want the shapefiles saved

os.chdir(path_to_csv)  # Sets current directory to path of csv files
for fname in glob.glob("*.csv"):  # Finds each .csv file and applies following actions
        uri = "file:///" + path_to_csv + fname + "?delimiter=%s&crs=epsg:4326&xField=%s&yField=%s" % (",", "x", "y")
        name = fname.replace('.csv', '')
        lyr = QgsVectorLayer(uri, name, 'delimitedtext')
        QgsMapLayerRegistry.instance().addMapLayer(lyr)  # Imports csv files to QGIS canvas (assuming 'X' and 'Y' fields exist)

crs = 'EPSG:32633'  # Set crs
shapefiles = QgsMapLayerRegistry.instance().mapLayers().values()  # Identifies loaded layers before transforming and updating 'X' and 'Y' fields
for shapes in shapefiles:
        outputs_0 = processing.runalg("qgis:reprojectlayer", shapes, crs, None)
        outputs_1 = processing.runalg("qgis:fieldcalculator", outputs_0['OUTPUT'], 'X', 0, 10, 10, False, '$x', None)
        outputs_2 = processing.runalg("qgis:fieldcalculator", outputs_1['OUTPUT_LAYER'], 'Y', 0, 10, 10, False, '$y', shape_result + shapes.name())

os.chdir(shape_result)  # Sets current directory to path of new shapefiles
for layer in glob.glob("*.shp"):  # Finds each .shp file and applies following actions
        new_layer = QgsVectorLayer(layer, os.path.basename(layer), "ogr")
        new_name = layer.replace('.shp', '')
        csvpath = "C:/Users/You/Desktop/Testing/CSV results/" + new_name + ".csv"  # Change path to where you want the csv(s) saved
        QgsVectorFileWriter.writeAsVectorFormat(new_layer, csvpath, 'utf-8', None, "CSV")

Hope this helps!

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