Adding wkt.csv file to QGIS 3 project using script

Question

I have written a plugin using the Plugin_Builder tool. It takes a CSV, rearranges it and adds a column of WKT coordinates in the style LINESTRING(x1 y1,x2 y2). It then writes it as a new .csv. This works fine. I can then manually import it as 'delimited text' and it loads as a normal visible, interrogatable layer. What I am trying to do is get the script to load the CSV into QGIS directly after creating the file. After writing the CSV to my chosen location (out_filename), I have added the following:

            ##adding the file to QGIS
            uri='out_filename?&wktField=%s'%("wkt")   
            #uri ='file:///C://Users//Desktop//test2.csv?delimiter=%s&crs=epsg:2154&wktField=%s' % (",", "WKT")
            layer = self.iface.addVectorLayer(uri, "my_layer", "delimitedtext")
            #QgsVectorFileWriter.writeAsVectorFormat(layer,out_filename + '.shp', 'CP1250', None, 'ESRI Shapefile')
            #QgsProject.instance().addMapLayer(layer)

The # lines are me trying experiments, none of which work. I wasn't sure if it was just not finding the file, hence the explicit name. A layer is loaded but with no contents. The QGIS error message is:

2022-06-04T14:09:44     WARNING    Errors in file C://Users//Desktop//test2.csv
2022-06-04T14:09:44     WARNING    File cannot be opened or delimiter parameters are not valid

The layer that is created has a red warning icon next to the name. If I click it and redirect it to the file location, it opens as expected.

The headers and first two rows look like:

Name,ID,Seq,Heading,Start time,End time,SOL Fix,EOL Fix,Wind,Waves,Format,Type,N/A,N/A,N/A,N/A,N/A,N/A,N/A,Nav,USBL,Comments,Status,Length,Project,Client,Area,Contractor,Vessel,Datum,EPSG,WKT
EQ22307-01001-04,1,,22.355,,,,,,,Prime,Analogue,-,-,-,-,-,-,-,-,-, ,Virgin,8.644,,,,,,ED50 - UTM 29N/-9E,,"LINESTRING(525182.750 6756568.136,528470.372 6764562.356)"
EQ22307-01005-08,2,,22.355,,,,,,,Prime,Analogue,-,-,-,-,-,-,-,-,-, ,Virgin,8.644,,,,,,ED50 - UTM 29N/-9E,,"LINESTRING(525205.871 6756558.628,528493.493 6764552.848)"

Answer 1

After learning how to import a X/Y point pairs, I rejigged the code to get it to work for WKT.CSV. I think my problem above was primarily the file path/uri. This code now works:

    uri="file:///"+out_filename+"?delimiter={}&wktField={}".format(",","WKT")
    vlayer = QgsVectorLayer(uri, project+"_QC", "delimitedtext")
    QgsProject.instance().addMapLayer(vlayer)
    my_crs=QgsProject.instance().crs().authid()
    vlayer.setCrs(QgsCoordinateReferenceSystem(my_crs))