Converting input into currency

Question

I've been set homework to create a calculator in Python that uses currency rather than just normal numbers. This is what I have so far:

import math

def add(x, y):
    return x+y

def subtract(x, y):
    return x-y

def multiply(x, y):
    return x*y

def divide(x, y):
    return x/y

print('select option')
print('1.add')
print('2.subtract')
print('3.multiply')
print('4.divide')

choice = input('enter choice (1/2/3/4): ')

if choice > '4':
    print('invalid choice, try again')

num1=float(input('enter first number: '))
num2=float(input('enter second number: '))

if choice == '1':
    print(num1, '+',num2, '=', add(num1,num2))
elif choice == '2':
    print(num1, '-',num2, '=', subtract(num1,num2))
elif choice == '3':
    print(num1, '*', num2, '=', multiply(num1,num2))
elif choice == '4':
    print(num1, '/', num2, '=', divide(num1,num2))`

How can I change the input into currency form, and then my output, too?