ERROR 4: Unable to open EPSG support file gcs.csv

Question

I am writing a standalone QGIS python application to run some unittests. I am getting an error when I try to use the QgsCoordinateReferenceSystem library.

ERROR 4: Unable to open EPSG support file gcs.csv. Try setting the GDAL_DATA 
environment variable to point to the directory containing EPSG csv files.

I am running QGIS 3.0.3 on Windows 7.

I have made sure my GDAL_DATA path points to the gdal folder containing the gcs.csv. I have even placed a print statement above and below the call to QgsCoordinateReferenceSystem to print the environment variable which is correct as C:\Program Files\QGIS 3.0\share\gdal.

Any insight into this would be most helpful.

my full code is:

import os
from qgis.core import QgsApplication, QgsCoordinateReferenceSystem

app = QgsApplication([], True)
app.setPrefixPath(r"C:\Program Files\QGIS 3.0\apps\qgis", True)
app.initQgis()

app.setPluginPath(app.pluginPath().replace("\n", ""))
app.setPkgDataPath(app.pkgDataPath().replace("\n", ""))

print(os.environ["GDAL_DATA"])
c = QgsCoordinateReferenceSystem(4326)
print(os.environ["GDAL_DATA"])

This Python script is called from the following batch file:

@ECHO OFF

call "C:\Program Files\QGIS 3.0\bin\o4w_env.bat"
call "C:\Program Files\QGIS 3.0\bin\qt5_env.bat"
call "C:\Program Files\QGIS 3.0\bin\py3_env.bat"

set PYTHONPATH=%OSGEO4W_ROOT%\apps\qgis\python;%OSGEO4W_ROOT%\apps\qgis\python\plugins;%USERPROFILE%\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins%PYTHONPATH%

python test.py

Answer 1

My GDAL_DATA environment variable was wrong, it had a line break (\n) at the end causing my error. I fixed it by forcefully changing the environment variable to remove the line break.

QgsApplication.instance().initQgis() appears to add line breaks to the end of all my environment paths. I have patched this by replacing the line break in each variable manually.

Please see complete code below:

import os
from qgis.core import QgsApplication, QgsCoordinateReferenceSystem

app = QgsApplication([], True)
app.setPrefixPath(r"C:\Program Files\QGIS 3.0\apps\qgis", True)
app.initQgis()

app.setPluginPath(app.pluginPath().replace("\n", ""))
app.setPkgDataPath(app.pkgDataPath().replace("\n", ""))

# With line break at the end
print(os.environ["GDAL_DATA"])

os.environ["GDAL_DATA"] = os.environ["GDAL_DATA"].replace("\n", "")
# Without line break
print(os.environ["GDAL_DATA"])

c = QgsCoordinateReferenceSystem(4326)

EDIT 6/6/2018 I found the problem to occur when after import qgis, this call seems to change the system variables. I have solved this by copying the environment variables before importing and then replacing them after.

import os

environment_variables = os.environ.copy()
import qgis
os.environ = environment_variables

from qgis.core import QgsApplication, QgsCoordinateReferenceSystem

app = QgsApplication([], True)
app.setPrefixPath(r"C:\Program Files\QGIS 3.0\apps\qgis", True)
app.initQgis()

c = QgsCoordinateReferenceSystem(4326)