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I am having trouble loading csv files into layers using QgsVectorLayer().

I know this looks like a repeat, but I have carefully read

Create a script to add delimited text layer in QGIS

and

http://hub.qgis.org/issues/7491

but still cannot get it work.

An example of my data file, test.csv:

Index,y,x
0,37.7646618,-122.4960858
1,37.777494,-122.416311
2,37.717707,-122.3997056
3,37.732284,-122.498118
4,37.749998,-122.392333

My code:

import os
import urllib

import pathlib
from qgis.core import QgsVectorLayer

local_path = 'C:\dev\FCMS_conflation\data\TMC_nodes.csv'
node_layer = 'test'

abspath = os.path.abspath(local_path)
params = {'delimiter': ',',
          'decimalPoint': '.',
          'xField': longitude,
          'yField': latitude}

uri = "%s?%s" %(pathlib.Path(abspath).as_uri(), urllib.unquote(urllib.urlencode(params)))

layer = QgsVectorLayer(uri, node_layer, "delimitedtext")

The formatted URI looks like:

[] uri
>>> 'file:///C:/dev/FCMS_conflation/data/TMC_nodes.csv?decimalPoint=.&delimiter=,&xField=longitude&yField=latitude'

I have tried many variations of the parameters, including the crs and type. But no matter what I try, I cannot create a valid layer.

[] layer.isValid()
>>> False

I have verified that I can add the file using the QGIS gui. I even tried using the uri provided by layer.metadata from within the Python plugin.

I am using QGIS 2.10.1 on Windows 7 64-bit machine.

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andrew
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  • Good question, where does node_layer come from? It should be a Qstring but I can't see where it's being set. Are you getting any error message? – Michael Stimson Sep 01 '15 at 01:02
  • I defined node_layer to just be a random string. I edited the code snip. Maybe I need to make a Qstring? – andrew Sep 01 '15 at 01:08
  • No error messages. It just doesn't pass the isValid test. – andrew Sep 01 '15 at 01:10
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    You're in python, QString is near enough to string (C would have a cow about the subtle difference). Perhaps it's the path that's the difficulty.. the example given doesn't start with file:///, perhaps just c:/dev...?decimal... like in the example. – Michael Stimson Sep 01 '15 at 01:48
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    It seems you need to set the QGIS prefix path, as I explain in http://gis.stackexchange.com/questions/144058/how-to-load-a-raster-layer-using-pyqgis/146513#146513 and http://gis.stackexchange.com/questions/155745/failed-to-create-memory-layers-in-qgis-application-on-linux/155852#155852 Please let me know if it solves your problem. – Germán Carrillo Sep 01 '15 at 03:13
  • @gcarrillo Thanks for the solution! I had to work on another project for a while I just got back to this. For my Windows 7 machine I had to use:

    qgis_prefix = u'C:/PROGRA~1/QGISPI~1/apps/qgis

     – andrew Sep 19 '15 at 23:19

1 Answers1

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It seems you need to set the QGIS prefix path, as I explain in Loading raster layer using PyQGIS? and Failed to create memory layers in QGIS application on Linux

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Germán Carrillo
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