Purpose of calling function without brackets python

Question

Consider the following:

class objectTest():

    def __init__(self, a):
        self.value = a

    def get_value(self):
        return self.value

class exec         


        

Answer 1

def mul(a, b):
    return a * b

def add(a, b):
    return a + b

def do(op, a, b):
    return op(a, b)

do(add, 2, 3)  # return 5