How to convert an integer to a string in any base?


Python allows easy creation of an integer from a string of a given base via

int(str, base). 

I want to perform the inverse: creation of a string from an integer, i.e. I want some function int2base(num, base), such that:

int(int2base(x, b), b) == x

The function name/argument order is unimportant.

For any number x and base b that int() will accept.

This is an easy function to write: in fact it"s easier than describing it in this question. However, I feel like I must be missing something.

I know about the functions bin, oct, hex, but I cannot use them for a few reasons:

  • Those functions are not available on older versions of Python, with which I need compatibility with (2.2)

  • I want a general solution that can be called the same way for different bases

  • I want to allow bases other than 2, 8, 16


Answer rating: 141

Surprisingly, people were giving only solutions that convert to small bases (smaller than the length of the English alphabet). There was no attempt to give a solution which converts to any arbitrary base from 2 to infinity.

So here is a super simple solution:

def numberToBase(n, b):
    if n == 0:
        return [0]
    digits = []
    while n:
        digits.append(int(n % b))
        n //= b
    return digits[::-1]

so if you need to convert some super huge number to the base 577,

numberToBase(67854 ** 15 - 102, 577), will give you a correct solution: [4, 473, 131, 96, 431, 285, 524, 486, 28, 23, 16, 82, 292, 538, 149, 25, 41, 483, 100, 517, 131, 28, 0, 435, 197, 264, 455],

Which you can later convert to any base you want