check particular feature exists using pyqgis

Question

I want to check that a particular features exists or not in getFeature().

Suppose in attribute table I have ID, Name, CAT, and Type columns. Now I want to check that CATEGORY column is exists or not in features.

I use this but this is not working.

for poi in layerPOI.getFeatures():
    if "CATEGORY"  in layerPOI.getFeatures():

and this as well. It producing keyError

if poi["CATEGORY"]#As category not exists it giving error here

Can you clarify how you want to check if it exists? Do you want to see if it contains a certain value or a specific value in a specific field...? — Joseph, Sep 30 '16 at 11:58
You could use some of the methods described in this post: How to read the attribute values using PyQGIS?. And add an if statement to see if the feature exists by matching it to an id or name. — Joseph, Sep 30 '16 at 12:04
what are the some of the methods. i have already used if it give me error in if condition — Muhammad Faizan Khan, Sep 30 '16 at 12:14
The term layerPOI.getFeatures() is an iterator and poi is a QgsFeature object. You cannot do if "CATEGORY" in layerPOI.getFeatures() again. — xunilk, Sep 30 '16 at 12:14
@xunilk so how to check that man. a particular feature name is exists in the features or not — Muhammad Faizan Khan, Sep 30 '16 at 12:15
@MohammadFaizanKhan - Could you please edit your question to show an example of what you mean exactly? — Joseph, Sep 30 '16 at 12:24

score 5 · Accepted Answer · answered Sep 30 '16 at 12:40

5

To check if 'CATEGORY' exists as a field:

layer = iface.activeLayer()

field = 'CATEGORY' 

index = layer.fieldNameIndex(field)

if index == -1:
    print "field doesn't exist"
else:
    print "field exists"

answered Sep 30 '16 at 12:40

xunilk

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check particular feature exists using pyqgis

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