Pythonic way to create a big random base-29 number

I'm creating a program which has to handle rather big ints in python. Ranging from 0-10⁴⁶⁷⁷. Internally, I represent them with as base-29 integers. Thus using the alfabet: 012345679ABCDEFGHIJKLMNOPQRS.

I created a function to create a random base-29 variable of any length in python. But is there a shorter, more pythonic way possible? (if this is even a proper way of doing it).

The function to create a random base-29 number:

import random

def random_base(base_number = 29, length = 10)
    alfabet = "012345679ABCDEFGHIJKLMNOPQRS"
    return [alfabet[random.randint(0,base_number - 1)] for _ in range(length)]

Thus, is there some built-in python function to perform this, or is this the way to go?

Please comment if things are unclear!

Thanks in Advance