Import a custom function from the python console

Question

I'm trying to import a custom function from the python console, but it return the error:

'QgsExpressionFunction' object is not callable

My example function (saved as function.py file in /.qgis2/python/ directory) is:

from qgis.core import *
from qgis.utils import qgsfunction
from qgis.core import QgsExpression
@qgsfunction(args="auto", group='Custom')
def TriangleArea(b,h,feature,parent):
 area = b*h/2.0
 return area
 QgsExpression.registerFunction(TriangleArea) 

To import and execute the function i use:

from function import *
A = TriangleArea(3, 5)
print A

what's wrong?

• Joseph: Is your function.py file saved in your /.qgis2/python/ directory?
• Domenico Fuoco: @Joseph, yes it is.

Answer 1

Try using the following where you can import your TriangleArea() function and then use the method function to run it:

from function import TriangleArea
A = TriangleArea.function(3, 5, None, None)
print A

The feature and parent parameters can be left empty.

Result

---

Another way is to import your file directly and then call your function:

import function
A = function.TriangleArea.function(3, 5, None, None)
print A

Result

---

Note: I strongly suggest you call your file something else to avoid confusion with the function method :)

• Domenico Fuoco: Sorry it doesn't work.
• Joseph: @DomenicoFuoco - Did you restart QGIS?
• Joseph: @DomenicoFuoco - Not necessarily because I used from function import TriangleArea which means I can call the function directly. You could use from function import * and then use A = function.TriangleArea.function(3, 5, None, None).
• Joseph: @DomenicoFuoco - I have edited the post with some screenshots because I think there's a little misunderstanding. Your filename is called function. But there is a method also called function() which is used to run TriangleArea. I strongly suggest you change your filename to something else to avoid confusion.
• Domenico Fuoco: I'm really sorry I knew badly. I followed your suggestion and the script works perfectly. Thank you

Answer 2

With @Joseph 's suggestions I created a function that opens a raster grid and passes the values into a numpy array. The procedure I have adopted is:

from qgis.core import *
from qgis.utils import qgsfunction
from qgis.core import QgsExpression
import numpy as np
@qgsfunction(args="auto", group='Custom')
def OpenGrid(GridPath, feature, parent):
 GridName = QgsRasterLayer(GridPath)
 # Create array 'values_GridName'
 provider = GridName.dataProvider()
 extent = provider.extent()
 rows = GridName.height()
 cols = GridName.width()
 xmin = extent.xMinimum()
 ymax = extent.yMaximum()
 xsize = GridName.rasterUnitsPerPixelX()
 ysize = GridName.rasterUnitsPerPixelY()
 block = provider.block(1, extent, cols, rows)
 values_GridName = [ [] for i in range(rows) ]
 for i in range(rows):
 for j in range(cols):
 block.value(i,j)
 values_GridName[i].append(block.value(i,j))
 #This code line is used to make sure all numbers are float type
 values_GridName = np.array(values_GridName, dtype = float)
 return values_GridName

The function was saved in /.qgis2/python/OpenRlayer.py.

I call the function with the following commands:

from OpenRlayer import OpenGrid 
grid_path = path/to/grid.asc
values_Grid = OpenGrid.function(grid_path, None, None)

This is how I created the array that contains the grid data and now I can do the operations I need