How to convert a number to the binary system consisting of 2 and 5?

Question

Python

The very essence of the problem is in the title. There is some number in the number system consisting of 2 and 5, for example 22. If you convert it to decimal, you get 3. The count starts from 2, that is: 2 - 1; 5 - 2 and so on. I was able to implement it like:

N = int(input())
print(str(int(str(N).replace('2', '0').replace('5', '1'), 2)))

Of course, it doesn't work correctly. When you enter 2, it outputs 0. When you enter 22, 222 and so on - the same. Is there an easy way to solve my problem? Library for custom number systems? And no looping at all. Glad for any answer

Answer 1

Converting a number to a binary string is bin(). The only thing is to tear off the first two characters of the 0b prefix. For more convenient replacement of several characters at once, it is better to use .translate(). As a result, we get:

table = {ord('0'):'2',ord('1'):'5'}
print(bin(N)[2:].translate(table))