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I'm writing a script that will iterate rasters and do some calculations on each raster. I would like the formula in the GDAL raster calculator to include a variable, which I read from a txt file. I don't want the user to insert the variable but to integrate it in the script.

The code of the raster calculator I use is this:

outputs_GDALOGRRASTERCALCULATOR_1=processing.runalg('gdalogr:rastercalculator', rlayer,'1',None,'1',None,'1',None,'1',None,'1',None,'1','10000*(A*0.00002-0.1)/sin(65)*(A>0.001)','0',4,None,outputName)

I need the number inside of the sin, in this example 65, to be a variable, so every time I'll have a different number.

Is that possible to integrate a variable in this syntax?

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You could use Python's .format() method to include reading a variable from a textfile. The following is a simple example of reading each line in a text file and then running the raster calculator on rlayer for each variable. This is assuming your text file looks like this:

65
90
120

etc.

f = open('path/to/file.txt')
lines = f.read().splitlines()
f.close()
for line in lines:
    outputs_GDALOGRRASTERCALCULATOR_1=processing.runalg('gdalogr:rastercalculator', rlayer,'1',None,'1',None,'1',None,'1',None,'1',None,'1','10000*(A*0.00002-0.1)/sin({})*(A>0.001)'.format(line),'0',4,None,outputName)
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    Thank you very much, it helped. Now I understand that the formula for calculation is actually a string and not numbers, so it is possible to create the desired string beforehand and then just add the string variable instead of the entire formula. Like that: syntax = '(A>0.001)*10000*(A*0.00002-0.1)/sin('+str(SUN_ELEVATION)+') outputs_GDALOGRRASTERCALCULATOR_1=processing.runalg('gdalogr:rastercalculator', rlayer,'1',None,'1',None,'1',None,'1',None,'1',None,'1',syntax,'0',4,None,outputName) – user88484 Feb 8 '17 at 8:37
  • @user88484 - Most welcome, glad it helped! And very nicely done :) – Joseph Feb 8 '17 at 10:40

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