using subroutines in python instead of if statements

Question

I was wondering if i could use a subroutine here instead if so how do i or is there a another way to shorten this piece of code.

    if currency1=='GBP':
        if currency2=='USD':
            number=float(1.64)
        elif currency2=='EUR':
            number=float(1.20552)
        elif currency2=='JPY':
            number=float(171.181)

Answer 1

You could certainly make a dictionary:

currencies = {}
currencies['USD'] = 1.64
currencies['EUR'] = 1.20552
currencies['JPY'] = 171.181
currencies['GBP'] = 1.

number = currencies[currency2]

what's great about this is you can also do:

other_number = currencies[currency1]
exchange_rate = number / other_number # exchange rate BETWEEN the two currencies