Converting numbers systems

def convertNumber(base, n, to):
    digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    decimal = 0

    if base > 36 or to > 36:
        print("Numbers based on systems grather than 36 are not supported")
        return

    for exponent, i in enumerate(str(n)[::-1]):
        if digits.index(i) >= base:
            print("Value {0} is not written in {1} based system, conversion impossible").format(n, base)
            return
        decimal += digits.index(i) * base ** exponent

    result = ""
    while decimal >= 1:
        result += digits[decimal % to]
        decimal /= to
    print result[::-1]

convertNumber(16, "DEAD", 10)
convertNumber(10, 57005, 16)