For theoretical background see this page.

Let $n$ be a positive number in decimal system and $k$ be the basis in which $n$ will be represented. The following code give us the representation of $n$ in basis $k$.

#!/usr/bin/python
 
def representation(n, k):
    (q, r) = (n // k, n % k)
 
    # print(str(n) + " = " + str(k) + " * " + str(q) + " + " + str(r))
    if q == 0:
        return [r]
    else:
        return representation(q, k) + [r]

Example: Let $n = 383$ and $k=4$.

n = 383
k = 4
 
print(''.join(map(str, representation(n, k))))

The solution is $11333$.