How to execute the function program in Python in a proper way?

[update, thanks to Richard]
There's nothing wrong with your program.
Actually there is an error in your code, as well spotted by Richard:

Quote:

a(number1,number2)
print(a)

Should be instead

result = a(number1,number2)
print(result)

[/update]

I would have written it this way

def introduction():
    print('this program will give you the result of multiplication, division and addition of two numbers')

def ask_num(prompt):
    n=int(input(prompt))
    return n

def add(num1,num2):
    result = num1 + num2
    return result

def pyt():
    introduction()
    #this will give you the two numbers
    number1 = ask_num( 'please enter the first no.')
    number2 = ask_num( 'please enter the second no.')
    result = add(number1, number2)
    print('the result is ' +  str(result))

pyt()

but it's just matter of taste.