""" Convert numbers from base 10 integers to base X strings and back again. Sample usage: >>> base20 = BaseConverter('0123456789abcdefghij') >>> base20.from_decimal(1234) '31e' >>> base20.to_decimal('31e') 1234 """ class BaseConverter(object): decimal_digits = "0123456789" def __init__(self, digits): self.digits = digits def from_decimal(self, i): return self.convert(i, self.decimal_digits, self.digits) def to_decimal(self, s): return int(self.convert(s, self.digits, self.decimal_digits)) def convert(number, fromdigits, todigits): # Based on http://code.activestate.com/recipes/111286/ if str(number)[0] == '-': number = str(number)[1:] neg = 1 else: neg = 0 # make an integer out of the number x = 0 for digit in str(number): x = x * len(fromdigits) + fromdigits.index(digit) # create the result in base 'len(todigits)' if x == 0: res = todigits[0] else: res = "" while x > 0: digit = x % len(todigits) res = todigits[digit] + res x = int(x / len(todigits)) if neg: res = '-' + res return res convert = staticmethod(convert) bin = BaseConverter('01') hexconv = BaseConverter('0123456789ABCDEF') base62 = BaseConverter( 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz' ) if __name__ == '__main__': nums = [-10 ** 10, 10 ** 10] + range(-100, 100) for convertor in [bin, hexconv, base62]: for i in nums: assert i == bin.to_decimal(bin.from_decimal(i)), '%s failed' % i