KeyError but field exists (PyQGIS)












2















I have 10 fields in my shapefile, and I want to use Python (3.7) to access the value of one field in QGIS.



When I run my code (below) I get a KeyError: '6' (index position of the field), implying that the field lookup worked, but that once I try to access the value, the field doesn't exist. 



f = layer.getFeature(fid)

index = layer.fields().lookupField('length')

print("length: ", f[index])


I also tried:



f = layer.getFeature(fid)

index = layer.fields().indexFromName('length')

print("length: ", f[index])


Both throw the same error.



Sample code uses just in a print statement, but I need to use the index number at various points/for different methods.






pyqgis







share|improve this question

























  • you are using indexand after is idx

    – Fran Raga
    4 hours ago











  • Try f.attributes()[idx] (qgis.org/api/… and gis.stackexchange.com/a/54059/2856)

    – user2856
    2 hours ago











  • @FranRaga corrected, just an error in my code transcribed here

    – jyingling
    14 mins ago
















2















I have 10 fields in my shapefile, and I want to use Python (3.7) to access the value of one field in QGIS.



When I run my code (below) I get a KeyError: '6' (index position of the field), implying that the field lookup worked, but that once I try to access the value, the field doesn't exist. 



f = layer.getFeature(fid)

index = layer.fields().lookupField('length')

print("length: ", f[index])


I also tried:



f = layer.getFeature(fid)

index = layer.fields().indexFromName('length')

print("length: ", f[index])


Both throw the same error.



Sample code uses just in a print statement, but I need to use the index number at various points/for different methods.






pyqgis







share|improve this question

























  • you are using indexand after is idx

    – Fran Raga
    4 hours ago











  • Try f.attributes()[idx] (qgis.org/api/… and gis.stackexchange.com/a/54059/2856)

    – user2856
    2 hours ago











  • @FranRaga corrected, just an error in my code transcribed here

    – jyingling
    14 mins ago














2












2








2








I have 10 fields in my shapefile, and I want to use Python (3.7) to access the value of one field in QGIS.



When I run my code (below) I get a KeyError: '6' (index position of the field), implying that the field lookup worked, but that once I try to access the value, the field doesn't exist. 



f = layer.getFeature(fid)

index = layer.fields().lookupField('length')

print("length: ", f[index])


I also tried:



f = layer.getFeature(fid)

index = layer.fields().indexFromName('length')

print("length: ", f[index])


Both throw the same error.



Sample code uses just in a print statement, but I need to use the index number at various points/for different methods.






pyqgis







share|improve this question
















I have 10 fields in my shapefile, and I want to use Python (3.7) to access the value of one field in QGIS.



When I run my code (below) I get a KeyError: '6' (index position of the field), implying that the field lookup worked, but that once I try to access the value, the field doesn't exist. 



f = layer.getFeature(fid)

index = layer.fields().lookupField('length')

print("length: ", f[index])


I also tried:



f = layer.getFeature(fid)

index = layer.fields().indexFromName('length')

print("length: ", f[index])


Both throw the same error.



Sample code uses just in a print statement, but I need to use the index number at various points/for different methods.






pyqgis




pyqgis






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 14 mins ago







jyingling

















asked 5 hours ago









jyinglingjyingling

106110




106110













  • you are using indexand after is idx

    – Fran Raga
    4 hours ago











  • Try f.attributes()[idx] (qgis.org/api/… and gis.stackexchange.com/a/54059/2856)

    – user2856
    2 hours ago











  • @FranRaga corrected, just an error in my code transcribed here

    – jyingling
    14 mins ago



















  • you are using indexand after is idx

    – Fran Raga
    4 hours ago











  • Try f.attributes()[idx] (qgis.org/api/… and gis.stackexchange.com/a/54059/2856)

    – user2856
    2 hours ago











  • @FranRaga corrected, just an error in my code transcribed here

    – jyingling
    14 mins ago

















you are using indexand after is idx

– Fran Raga
4 hours ago





you are using indexand after is idx

– Fran Raga
4 hours ago













Try f.attributes()[idx] (qgis.org/api/… and gis.stackexchange.com/a/54059/2856)

– user2856
2 hours ago





Try f.attributes()[idx] (qgis.org/api/… and gis.stackexchange.com/a/54059/2856)

– user2856
2 hours ago













@FranRaga corrected, just an error in my code transcribed here

– jyingling
14 mins ago





@FranRaga corrected, just an error in my code transcribed here

– jyingling
14 mins ago










2 Answers
2






active

oldest

votes


















2














The solution is simpler:



print("length: ", f['length'])





share|improve this answer
























  • The goal of my code is not actually to print the value, I need to use other methods that require an index value and are also throwing the key error.

    – jyingling
    5 hours ago











  • @jyingling please update the question to reflect this requirement

    – underdark♦
    5 hours ago



















1














Use this



print("length: ", f.attributes()[index])


or loop all features



layer = iface.activeLayer()             

index = layer.fields().indexFromName('length')

for f in layer.getFeatures():

    print (f.attributes()[index])





share|improve this answer


























  • Threw IndexError: list index out of range

    – jyingling
    7 mins ago











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









2














The solution is simpler:



print("length: ", f['length'])





share|improve this answer
























  • The goal of my code is not actually to print the value, I need to use other methods that require an index value and are also throwing the key error.

    – jyingling
    5 hours ago











  • @jyingling please update the question to reflect this requirement

    – underdark♦
    5 hours ago
















2














The solution is simpler:



print("length: ", f['length'])





share|improve this answer
























  • The goal of my code is not actually to print the value, I need to use other methods that require an index value and are also throwing the key error.

    – jyingling
    5 hours ago











  • @jyingling please update the question to reflect this requirement

    – underdark♦
    5 hours ago














2












2








2







The solution is simpler:



print("length: ", f['length'])





share|improve this answer













The solution is simpler:



print("length: ", f['length'])






share|improve this answer












share|improve this answer



share|improve this answer










answered 5 hours ago









underdark♦underdark

68.1k13177341




68.1k13177341













  • The goal of my code is not actually to print the value, I need to use other methods that require an index value and are also throwing the key error.

    – jyingling
    5 hours ago











  • @jyingling please update the question to reflect this requirement

    – underdark♦
    5 hours ago



















  • The goal of my code is not actually to print the value, I need to use other methods that require an index value and are also throwing the key error.

    – jyingling
    5 hours ago











  • @jyingling please update the question to reflect this requirement

    – underdark♦
    5 hours ago

















The goal of my code is not actually to print the value, I need to use other methods that require an index value and are also throwing the key error.

– jyingling
5 hours ago





The goal of my code is not actually to print the value, I need to use other methods that require an index value and are also throwing the key error.

– jyingling
5 hours ago













@jyingling please update the question to reflect this requirement

– underdark♦
5 hours ago





@jyingling please update the question to reflect this requirement

– underdark♦
5 hours ago













1














Use this



print("length: ", f.attributes()[index])


or loop all features



layer = iface.activeLayer()             

index = layer.fields().indexFromName('length')

for f in layer.getFeatures():

    print (f.attributes()[index])





share|improve this answer


























  • Threw IndexError: list index out of range

    – jyingling
    7 mins ago
















1














Use this



print("length: ", f.attributes()[index])


or loop all features



layer = iface.activeLayer()             

index = layer.fields().indexFromName('length')

for f in layer.getFeatures():

    print (f.attributes()[index])





share|improve this answer


























  • Threw IndexError: list index out of range

    – jyingling
    7 mins ago














1












1








1







Use this



print("length: ", f.attributes()[index])


or loop all features



layer = iface.activeLayer()             

index = layer.fields().indexFromName('length')

for f in layer.getFeatures():

    print (f.attributes()[index])





share|improve this answer















Use this



print("length: ", f.attributes()[index])


or loop all features



layer = iface.activeLayer()             

index = layer.fields().indexFromName('length')

for f in layer.getFeatures():

    print (f.attributes()[index])






share|improve this answer














share|improve this answer



share|improve this answer








edited 4 hours ago

























answered 4 hours ago









Fran RagaFran Raga

2,990919




2,990919













  • Threw IndexError: list index out of range

    – jyingling
    7 mins ago



















  • Threw IndexError: list index out of range

    – jyingling
    7 mins ago

















Threw IndexError: list index out of range

– jyingling
7 mins ago





Threw IndexError: list index out of range

– jyingling
7 mins ago


















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