Calculating field with ArcPy cursor?

Question

I am trying to calculate field with the formula. I tried arcpy.calculate field management but still having difficulty.

(10/10.4*(100*(math.exp(0.000871* !A!)-1+math.exp(0.000537* !B! )-1+math.exp(0.000487* !C! )-1)))

I used the below code.

with arcpy.da.UpdateCursor(fc, (VALUE, A, B, C)) as cursor: for row in cursor: row[0] = (10/10.4*(100*(math.exp(0.000871* !A!)-1+math.exp(0.000537* !B! )-1+math.exp(0.000487* !C! )-1))) cursor.updateRow()

Answer 1

#You need to reference each Field its Index in your list of Fields.
# what values are in A,B,C? string, integer,double? you may need to cast them

with arcpy.da.UpdateCursor(fc, ['VALUE', 'A', 'B', 'C']) as cursor: 
        for row in cursor:
            calc_a = math.exp(0.000871* row[1])-1
            calc_b = math.exp(0.000871* row[2])-1
            calc_c = math.exp(0.000871* row[3])-1
            row[0] = (10/10.4 * (100* (calc_a + calc_b + calc_c))))
            cursor.updateRow()