Calculate

from girs.rast.math_op import calculate
r_out = calculate('(A+B)/2',
                  A='D:/tmp/chirps/chirps-v2.0.2016.01.10.tif',
                  B='D:/tmp/chirps/chirps-v2.0.2016.01.11.tif',
                  output_raster='D:/tmp/calc.tif')