Multiple extract by attribute using PyQGIS

Question

I am trying to extract only three polygons from my attribute table from a vector layer. The column which contains the values I want is called "ID".

import processing

layer = r'C:\mypath....\mylayer.shp'
output = r'C:\mypath....\out.shp'

parameters = {'INPUT': layer, 'FIELD':'ID', 'OPERATOR':'7', 'VALUE': ['08008:0:0:8:81:3' and '08008:0:0:8:81:5' and '08008:0:0:8:89:1'], 'OUTPUT': output}
feedback = QgsProcessingFeedback()

processing.runAndLoadResults('native:extractbyattribute',
                            parameters,
                            feedback=feedback
                            )

This code gives me a new layer with the same attribute table as the original. I know the problem is related to 'VALUE' list, but don't know how to write the correct one.

Answer 1

Use extract by expression with parentheses and escape backslashes in front of each values single quote:

input = r'/home/bera/GIS/Data/testdata/ak_riks.shp'
output = r'/home/bera/Desktop/gistemp/ok_jl_riks_extracted.shp'

processing.run("native:extractbyexpression", 
    {'INPUT':input,
    'EXPRESSION':' "KOM_KOD" IN( \'2510\' , \'2523\' , \'2584\' )',
    'OUTPUT':output})

I executed the command manually then pressed Ctrl+Alt+H to see the syntax

Answer 2

You can use GRASS > Vector > v.extract tool (see documentation).

layer = r'C:\mypath....\mylayer.shp'
output = r'C:\mypath....\out.shp'

processing.runAndLoadResults("grass7:v.extract",
                             {'input': layer,
                              'where': "ID IN (0, 1, 2, 3)", # specify IDs
                              'type': [0,1,3,4,5],
                              'output': output})

If field type of ID is string, us this for where:

'where':"ID IN ('0', '1', '2', '3')"