Create a point layer from CSV using Python console in QGIS?

Question

I'd like to transfer manual processing steps to a python script. Though I'm not used to python yet.

The steps I do in QGIS:

1. Loading csv via right click in browser window into layer window.
2. the loaded table contains the coordinates in one column called "coords_lat_long". therefore, I split those coordinates in the Field Calculator using "lat" = left("coords_lat_long", strpos("coords_lat_long", ',')-1) and "long" = right("coords_lat_long", strpos("coords_lat_long", ',')-1)
3. after saving that, I load the csv again using "Add Tab Delimited Layer", tab separated with x-value = long and y-value = lat and WGS84
4. Then I export the layer to an existing GeoPackage and change the reference system to EPSG:2056 LV95.
5. Finally I'll have my point layer.

However, how can I transfer those steps into a python script?

What I have so far but can't extract lat and long:

uri = "thePathToMyCSV.csv"
csv_layer = iface.addVectorLayer(uri, "Standort_table", "ogr")
for field in csv_layer.fields():
    print(field.name())

f = QgsFeature()
csv_layer.startEditing()
lat_value = 'lat'
csv_layer.addAttribute(QgsField(lat_value, QVariant.Double))
long_value = 'long'
csv_layer.addAttribute(QgsField(long_value, QVariant.Double))
csv_layer.updateFields()

exp1 = QgsExpression('strpos("coords_lat_long", \',\')')
exp3 = QgsExpression('left(coords_lat_long, exp1)-1)')
exp4 = QgsExpression('right(coords_lat_long, exp1)-1)')

context = QgsExpressionContext()
context.appendScopes(QgsExpressionContextUtils.globalProjectLayerScopes(csv_layer))

with edit(csv_layer):
    for f in csv_layer.getFeatures():
        context.setFeature(f)
        f['lat'] = exp3.evaluate(context)
        f['long'] = exp4.evaluate(context)
        csv_layer.updateFeature(f)

Answer 1

You can use numpy.loadtxt() method to get the coordinates from the csv file.

import numpy as np

file_path = "/home/es/Documents/a.csv"
data = np.loadtxt(file_path, delimiter=",", skiprows=1)

iface.newProject()
uri = "Point?crs=EPSG:4326&field=lat:double&field=lon:double&index=yes"
layer = QgsVectorLayer(uri, "Layer", "memory")
QgsProject.instance().addMapLayer(layer)

for r in data:
    f = QgsFeature(layer.fields())
    f["lat"] = float(r[0])
    f["lon"] = float(r[1])

    geom = QgsGeometry.fromPointXY(QgsPointXY(r[0], r[1]))
    f.setGeometry(geom)

    layer.dataProvider().addFeatures([f])

layer.updateExtents()

Answer 2

So if you have these points:

This is what I would do. I have edited my code so it can capture your coordinates column regardless of the index:

# Import modules
import csv
from qgis.core import *
from qgis.utils import *

# create empty list for poits
coords = []
input_csv = r"\Path\to\Points.csv"

#read data from csv file and store in lists
with open(input_csv, 'r') as f:
   # create a dict reader
   reader = csv.DictReader(f)
   for row in reader:
       # split coord
       lat = row["coords_lat_long"].split(",")[0]
       lon = row["coords_lat_long"].split(",")[1]
       # append point
       coords.append(QgsPoint(float(lon),float(lat)))

# Begin a new project
iface.newProject()
# Create a QgsFeature for every point(coord pair)
feats = [ QgsFeature() for i in range(len(coords)) ]

for i, feat in enumerate(feats):
    feat.setGeometry(coords[i])
   
# Create a memory layer
layer = QgsVectorLayer(
    "Point?crs=epsg:4326&index=yes",
    "temporary_points",
    "memory"
)
# Add the layer
QgsProject.instance().addMapLayer(layer)
# Add the feature to the layer provider
pr = layer.dataProvider()
pr.addFeatures(feats)

I have created a memory layer but you can export to Geopackage. After that, all you need to do is re-project the file to your desired CRS.