Selecting layer by expression with two variables using PyQGIS

Question

I would like to filter a column coming from a layer with the command layer.selectByExpression().

I would like to leave the name of the column as a variable (not fixed). I made a conditions inside the column and its works very well, but I can't enter the column name as a variable.

That is the function which I am using:

layer.selectByExpression('\"column_name\"{}'.format(condition))

and here is my code:

class Layer_filter:
def __init__(self, name_layer, name_column, condition):
    self.name_layer = name_layer
    self.name_column = name_column
    self.condition = condition
    layer = QgsProject.instance().mapLayersByName(self.name_layer)[0]
    iface.setActiveLayer(layer)
    layer.selectByExpression('\&quot;column_name&quot;{}'.format(self.condition), QgsVectorLayer.SetSelection)

Taras · Accepted Answer · 2022-11-04T13:52:10.890

1

I hope I got the gist of the question correctly. Please, try this:

layer = QgsProject.instance().mapLayersByName('layer')[0]
target_field = 'Type' #layer.attributeDisplayName(1)
condition = 'Type 2'
if target_field in layer.fields().names():
    layer.selectByExpression(f"&quot;{target_field}&quot;='{condition}'")

References:

edited Nov 04 '22 at 13:52

answered Nov 04 '22 at 12:30

Taras

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in your code you write the name of the column and it is fixed by the function name_column = layer.attributeDisplayName(1). This function delivers the name of the second column. What I want to realize is to be able to enter a variable, which has to be equal to some name of a column, and with this value to be able to realize a condition. – Paulo Matias Montecinos Medel Nov 04 '22 at 13:02
yes, a user enters this variable – Paulo Matias Montecinos Medel Nov 04 '22 at 13:38
1

Thank you!. It has worked! – Paulo Matias Montecinos Medel Nov 04 '22 at 15:57
Always welcome! – Taras Nov 04 '22 at 18:14

Selecting layer by expression with two variables using PyQGIS

1 Answers1