I am working on a deduct amount function and it should raise a run time error if a < b in value:
here is my code
def deduct_amount(a, b):
    try:
        b - a < 0
    except ValueError:
        print(a + ' can not be less than' + b)
    else:
        c = a - b
        return c
deduct_amount(8, 12)
I know my try statement is faulty. how can I throw a value error if a is less than b
 
    