I have mentioned my QGIS script below. In that script, I have used "if condition".

When I open QGIS and run the script first time, after selecting the "Coordinate_System_SLD_99", it works accurately.

When I run it a second time, if I select "Coordinate_System_Kadawala" option, output comes according to the "Coordinate_System_SLD_99" option.

Once I close and reopen QGIS, it works accurately.

When I run the program again after selecting another option, same problem arise.

Can anyone help me to solve this?

##Dxf_to_Polygon(With Meta Data)=name
##Shape_File_Name=output vector
outputs_GRASS7V_IN_DXF_1=processing.runalg('grass7:v.in.dxf', Dxf_file,'1',True,False,True,False,False,True,'200000.000000,700000.000000,200000.000000,700000.000000',0,None)
outputs_GRASS7V_CLEAN_1=processing.runalg('grass7:v.clean', outputs_GRASS7V_IN_DXF_1['output'],1,0.1,'200000.000000,700000.000000,200000.000000,700000.000000',-1.0,0.0001,None,None)
outputs_QGISPOLYGONIZE_1=processing.runalg('qgis:polygonize', outputs_GRASS7V_CLEAN_1['output'],True,True,None)
outputs_SAGAPOLYGONDISSOLVEBYATTRIBUTE_1=processing.runalg('saga:polygondissolvebyattribute', outputs_QGISPOLYGONIZE_1['OUTPUT'],'area','layer','perimeter',False,None)
outputs_SAGAPOLYGONDISSOLVEALLPOLYGONS_1=processing.runalg('saga:polygondissolveallpolygons', outputs_SAGAPOLYGONDISSOLVEBYATTRIBUTE_1['DISSOLVED'],False,None)
outputs_QGISADDFIELDTOATTRIBUTESTABLE_1=processing.runalg('qgis:addfieldtoattributestable', outputs_SAGAPOLYGONDISSOLVEALLPOLYGONS_1['DISSOLVED'],'Req_No',2,30.0,0.0,None)
outputs_QGISADDFIELDTOATTRIBUTESTABLE_2=processing.runalg('qgis:addfieldtoattributestable', outputs_QGISADDFIELDTOATTRIBUTESTABLE_1['OUTPUT_LAYER'],'Surveyor_Name',2,25.0,0.0,None)
outputs_QGISADDFIELDTOATTRIBUTESTABLE_3=processing.runalg('qgis:addfieldtoattributestable', outputs_QGISADDFIELDTOATTRIBUTESTABLE_2['OUTPUT_LAYER'],'Survey_Date',2,20.0,0.0,None)
outputs_QGISADDFIELDTOATTRIBUTESTABLE_4=processing.runalg('qgis:addfieldtoattributestable', outputs_QGISADDFIELDTOATTRIBUTESTABLE_3['OUTPUT_LAYER'],'Plan_Name',2,20.0,0.0,None)
outputs_QGISADDFIELDTOATTRIBUTESTABLE_5=processing.runalg('qgis:addfieldtoattributestable', outputs_QGISADDFIELDTOATTRIBUTESTABLE_4['OUTPUT_LAYER'],'Method',2,20.0,0.0,None)
outputs_QGISADDFIELDTOATTRIBUTESTABLE_6=processing.runalg('qgis:addfieldtoattributestable', outputs_QGISADDFIELDTOATTRIBUTESTABLE_5['OUTPUT_LAYER'],'Cordi_Sys',2,20.0,0.0,None)
outputs_QGISADDFIELDTOATTRIBUTESTABLE_7=processing.runalg('qgis:addfieldtoattributestable', outputs_QGISADDFIELDTOATTRIBUTESTABLE_6['OUTPUT_LAYER'],'Purpose',2,20.0,0.0,None)

**if Coordinate_System_SLD_99 == True:
elif Coordinate_System_Kadawala == True:
       processing.runalg('qgis:reprojectlayer', outputs_QGISADDFIELDTOATTRIBUTESTABLE_7['OUTPUT_LAYER'],'EPSG:5234',Shape_File_Name)**

# #outputs_QGISREPROJECTLAYER_1=processing.runalg('qgis:reprojectlayer',outputs_QGISADDFIELDTOATTRIBUTESTABLE_7['OUTPUT_LAYER'],'EPSG:5235',Shape_File_Name)
#outputs_QGISREPROJECTLAYER_1=processing.runalg('qgis:reprojectlayer',               outputs_QGISADDFIELDTOATTRIBUTESTABLE_7['OUTPUT_LAYER'],'EPSG:5234',           Shape_File_Name)

from PyQt4.QtCore import QVariant
from qgis.utils import iface

import qgis
from qgis.core import *
from PyQt4.QtCore import *
#vl = iface.activeLayer()----->this is the corret code
#vl = qgis.utils.iface.activeLayer()
vl = processing.getObject(Shape_File_Name)
for field in vl.fields():
    print field.name()

metafile= processing.getObject(Meta_Data_File)
features = metafile.getFeatures()
for feat in features:
    attrs = feat.attributes()

features = vl.getFeatures() 
for feat in features:
    attrs = feat.attributes()
    print attrs[1]
    print attrs[2]
    print attrs[3]
    print attrs[4]

selection=vl.getFeatures(QgsFeatureRequest().setFilterExpression(' "OID"=0'))
for feat in selection:
  vl.changeAttributeValue(feat.id(),1, b[1])
  vl.changeAttributeValue(feat.id(),2, b[10])
  vl.changeAttributeValue(feat.id(),3, b[6])
  vl.changeAttributeValue(feat.id(),4, b[3])
  vl.changeAttributeValue(feat.id(),5, b[8])
  vl.changeAttributeValue(feat.id(),6, b[9])
  vl.changeAttributeValue(feat.id(),7, b[2])
 #selection=vl.getFeatures(QgsFeatureRequest().setFilterExpression(' "Req_No"= 5'))
#for feat in selection:
  #vl.changeAttributeValue(feat.id(),1, '45')

3 Answers 3


Once i open the QGIS,default OTF was wgs 84 EPSG:4326.At the very first,when i run my script,after selecting Coordinate_System as SLD_99, the OTF at the bottom of the QGIS window changed in to EPSG:5235 automatically.Once i save my out put as a KML file,out put of the KML positioned at the correct place in our country map.Then again when i run the script,by selecting the coordinate system as Kandawala,OTF didn't change into EPSG:5234. It exist as EPSG:5235 .Once i create a kml from the output, it does not positioned at the correct place.Actually,that was my problem.

To overcome that issue what i did was, before change the coordinate system in my sript,I change the OTF at the bottom of the QGIS window,according to the coordinate system which i am going to select in my script.That means ,if i select Kandawala in my script,i change OTF into EPSG:5234.Then result kml positioned at the correct place.

Above two answers are correct.It helps to assign coordinates system into my shape file automatically.But i feel, i have not convey may problem properly.I apologize for it.Anyway both your answers help me to over come a half of my problem.Thank both of you again for your valuable thoughts.


I think a more effective method would be to create a drop-down list and allow the user to select the CRS instead of using two booleans:

Drop-down list

In your script, replace the following:



##Coordinate_system=selection SLD_99;Kadawala

This drop-down list returns an integer value (i.e. 0 for the first item, 1 for the second item etc.). So for your if statement, you could use the following logic:

if Coordinate_system == 0:
    processing.runalg('qgis:reprojectlayer', outputs_QGISADDFIELDTOATTRIBUTESTABLE_7['OUTPUT_LAYER'],'EPSG:5234',Shape_File_Name)
  • @ShanakaHerath - Near the beginning of your code, you need to remove the boolean parameters (##Coordinate_System_SLD_99=boolean ##Coordinate_System_Kadawala=boolean) and add ##Coordinate_system=selection SLD_99;Kadawala. Save the script then run it, you should see the list menu from the interface.
    – Joseph
    Aug 21, 2018 at 10:45
  • still problem exist.It will work once i close the qgis and reopen only.then again it will not work for the other option Aug 21, 2018 at 11:06
  • @ShanakaHerath - Apologies but I can't replicate your problem. A simple script works for me, tested on QGIS 2.18.17 on Win7 64-bit.
    – Joseph
    Aug 21, 2018 at 12:57
  • Anyway, thanks a lot for the interest shown regarding my question. highly appreciate. I am using QGIS 2.18.19 on win 7 64-bit. Aug 21, 2018 at 14:58

When you select a coordinate system, make sure to set the boolean value of the other coordinate system variable to false.

--> when selecting Coordinate_System_Kadawala, set Coordinate_System_SLD_99 to false

  • i normally do it.thought i do it ,it gives that wrong result Aug 21, 2018 at 10:14

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