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Summing field values with PyQGIS

Summing values from different intersecting/overlapping points in QGISQGIS: SQL query within python console to sum a column based on values of other two columnsSum new values to existing attribute values in PyQGIS?PyQgis - Adding attributes to a POSTGIS layerWhy do I get different results from PyQGIS feature.geometry().type()?Why is QgsFeatureIterator returning bad data?Why can't I multiply values from column named 'length' using field calculator via PyQGIS?Adding field to shp subset layer using PyQGIS?How to get the selected value in a value map with Function Editor in QGIS 3.0.2?Summing attribute values of overlapping polyline portions in ArcGIS Desktop?Summing values from multiple polygons per neighbourhood in QGIS?Summing attribute values of overlapping polyline portions in QGIS 3.0.3Creating and updating a field from calculation

1

In QGIS 2.18 there is a shapefile with three fields accordingly

"id" | "Type" | "Value"

A sample of data: download

I want to get the total sum of all values in the field "Value". How can I achieve that in Python console?

Field "Value" maintains two types of data int() and NULL.

I was trying with a while-loop but it does not work

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total = 0

        index = 0

        while index < layer.featureCount():

            total = total + int(attr)

            index = index + 1

return(total)

Moreover, after executing @ahmadhanb's solution I received a correct number but
somehow with a strange output type, when print (type(sum(total))) it gives me
<type 'NoneType'>. What could be a problem?

How to achieve one number that gives the total sum of a whole field exclusive NULL-values?

References:

• Find Neighbor Polygons in a Layer


• Summing values from different intersecting/overlapping points in QGIS


• Sum new values to existing attribute values in PyQGIS?


• QGIS: SQL query within python console to sum a column based on values of other two columns

pyqgis sum

share|improve this question

edited 4 mins ago

Taras

asked 17 hours ago

TarasTaras

2,1922624

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Try to place the print(total) out of the loop. This will give you one value which is the total value.
  
  – ahmadhanb
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It gives one value, but a wrong one...
  
  – Taras
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  sum(filter(None,[f['Value'] for f in layer.getFeatures()]))
  
  – BERA
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Taras you can replace print(0) with continue to skip null values.
  
  – ahmadhanb
  17 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Thank you @ahmadhanb. Sorted with continue
  
  – Taras
  17 hours ago
  
  
  

  
  
  
  

 | 
show 3 more comments

1

In QGIS 2.18 there is a shapefile with three fields accordingly

"id" | "Type" | "Value"

A sample of data: download

I want to get the total sum of all values in the field "Value". How can I achieve that in Python console?

Field "Value" maintains two types of data int() and NULL.

I was trying with a while-loop but it does not work

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total = 0

        index = 0

        while index < layer.featureCount():

            total = total + int(attr)

            index = index + 1

return(total)

Moreover, after executing @ahmadhanb's solution I received a correct number but
somehow with a strange output type, when print (type(sum(total))) it gives me
<type 'NoneType'>. What could be a problem?

How to achieve one number that gives the total sum of a whole field exclusive NULL-values?

References:

• Find Neighbor Polygons in a Layer


• Summing values from different intersecting/overlapping points in QGIS


• Sum new values to existing attribute values in PyQGIS?


• QGIS: SQL query within python console to sum a column based on values of other two columns

pyqgis sum

share|improve this question

edited 4 mins ago

Taras

asked 17 hours ago

TarasTaras

2,1922624

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Try to place the print(total) out of the loop. This will give you one value which is the total value.
  
  – ahmadhanb
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It gives one value, but a wrong one...
  
  – Taras
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  sum(filter(None,[f['Value'] for f in layer.getFeatures()]))
  
  – BERA
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Taras you can replace print(0) with continue to skip null values.
  
  – ahmadhanb
  17 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Thank you @ahmadhanb. Sorted with continue
  
  – Taras
  17 hours ago
  
  
  

  
  
  
  

 | 
show 3 more comments

In QGIS 2.18 there is a shapefile with three fields accordingly

"id" | "Type" | "Value"

A sample of data: download

I want to get the total sum of all values in the field "Value". How can I achieve that in Python console?

Field "Value" maintains two types of data int() and NULL.

I was trying with a while-loop but it does not work

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total = 0

        index = 0

        while index < layer.featureCount():

            total = total + int(attr)

            index = index + 1

return(total)

Moreover, after executing @ahmadhanb's solution I received a correct number but
somehow with a strange output type, when print (type(sum(total))) it gives me
<type 'NoneType'>. What could be a problem?

How to achieve one number that gives the total sum of a whole field exclusive NULL-values?

References:

• Find Neighbor Polygons in a Layer


• Summing values from different intersecting/overlapping points in QGIS


• Sum new values to existing attribute values in PyQGIS?


• QGIS: SQL query within python console to sum a column based on values of other two columns

pyqgis sum

share|improve this question

edited 4 mins ago

Taras

asked 17 hours ago

TarasTaras

2,1922624

"id" | "Type" | "Value"

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total = 0

        index = 0

        while index < layer.featureCount():

            total = total + int(attr)

            index = index + 1

return(total)

share|improve this question

edited 4 mins ago

Taras

asked 17 hours ago

TarasTaras

2,1922624

share|improve this question

edited 4 mins ago

Taras

asked 17 hours ago

TarasTaras

2,1922624

asked 17 hours ago

TarasTaras

2,1922624

asked 17 hours ago

TarasTaras

2,1922624

1 Answer
1

active

oldest

votes

1

In fact your code provides a double number to the actual value. For example, if the total number is 50, your code provides 100. I think the correct code should be something like this:

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



total = []

for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total.append((int(attr)))

print(sum(total))

Add a total empty list outside the loop, and if the attr == NULL, it will skip the null values, and if there is a value in the attr it will be appended to the list. Then you can print the sum of the list outside the loop to get one value only.

Here is the screenshot of the output:

share|improve this answer

edited 16 hours ago

answered 17 hours ago

ahmadhanbahmadhanb

22.8k32153

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Looks promising! The problem is that the output of print(type(sum(total))) is <type 'NoneType'>. I need to use it in some further calculations.
  
  – Taras
  16 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Taras But I did not write print(type(sum(total))), I wrote print(sum(total)) which will provide an integer value. The output print(type(sum(total))) is <class 'int'> not <type 'NoneType'>
  
  – ahmadhanb
  16 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  How can I use this value in my further calculations when the type that I do have is <type 'NoneType'>?
  
  – Taras
  16 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That is strange. Why do you get <type 'NoneType'>? I am getting integer output type.
  
  – ahmadhanb
  16 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Shouldnt if attr == NULL be if attr is None?
  
  – BERA
  16 hours ago
  
  
  

  
  
  
  

 | 
show 1 more comment

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1

In fact your code provides a double number to the actual value. For example, if the total number is 50, your code provides 100. I think the correct code should be something like this:

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



total = []

for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total.append((int(attr)))

print(sum(total))

Add a total empty list outside the loop, and if the attr == NULL, it will skip the null values, and if there is a value in the attr it will be appended to the list. Then you can print the sum of the list outside the loop to get one value only.

Here is the screenshot of the output:

share|improve this answer

edited 16 hours ago

answered 17 hours ago

ahmadhanbahmadhanb

22.8k32153

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Looks promising! The problem is that the output of print(type(sum(total))) is <type 'NoneType'>. I need to use it in some further calculations.
  
  – Taras
  16 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Taras But I did not write print(type(sum(total))), I wrote print(sum(total)) which will provide an integer value. The output print(type(sum(total))) is <class 'int'> not <type 'NoneType'>
  
  – ahmadhanb
  16 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  How can I use this value in my further calculations when the type that I do have is <type 'NoneType'>?
  
  – Taras
  16 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That is strange. Why do you get <type 'NoneType'>? I am getting integer output type.
  
  – ahmadhanb
  16 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Shouldnt if attr == NULL be if attr is None?
  
  – BERA
  16 hours ago
  
  
  

  
  
  
  

 | 
show 1 more comment

1

In fact your code provides a double number to the actual value. For example, if the total number is 50, your code provides 100. I think the correct code should be something like this:

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



total = []

for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total.append((int(attr)))

print(sum(total))

Add a total empty list outside the loop, and if the attr == NULL, it will skip the null values, and if there is a value in the attr it will be appended to the list. Then you can print the sum of the list outside the loop to get one value only.

Here is the screenshot of the output:

share|improve this answer

edited 16 hours ago

answered 17 hours ago

ahmadhanbahmadhanb

22.8k32153

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Looks promising! The problem is that the output of print(type(sum(total))) is <type 'NoneType'>. I need to use it in some further calculations.
  
  – Taras
  16 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Taras But I did not write print(type(sum(total))), I wrote print(sum(total)) which will provide an integer value. The output print(type(sum(total))) is <class 'int'> not <type 'NoneType'>
  
  – ahmadhanb
  16 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  How can I use this value in my further calculations when the type that I do have is <type 'NoneType'>?
  
  – Taras
  16 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That is strange. Why do you get <type 'NoneType'>? I am getting integer output type.
  
  – ahmadhanb
  16 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Shouldnt if attr == NULL be if attr is None?
  
  – BERA
  16 hours ago
  
  
  

  
  
  
  

 | 
show 1 more comment

In fact your code provides a double number to the actual value. For example, if the total number is 50, your code provides 100. I think the correct code should be something like this:

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



total = []

for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total.append((int(attr)))

print(sum(total))

Add a total empty list outside the loop, and if the attr == NULL, it will skip the null values, and if there is a value in the attr it will be appended to the list. Then you can print the sum of the list outside the loop to get one value only.

Here is the screenshot of the output:

share|improve this answer

edited 16 hours ago

answered 17 hours ago

ahmadhanbahmadhanb

22.8k32153

layer = qgis.utils.iface.activeLayer()



if not layer.isValid():

    raise Exception('Layer is not valid')



features = layer.getFeatures()



total = []

for feat in features:

    attr = feat.attributes()[2]



    if attr == NULL:

        continue



    else:

        total.append((int(attr)))

print(sum(total))

share|improve this answer

edited 16 hours ago

answered 17 hours ago

ahmadhanbahmadhanb

22.8k32153

answered 17 hours ago

ahmadhanbahmadhanb

22.8k32153

answered 17 hours ago

ahmadhanbahmadhanb

22.8k32153