Created
May 9, 2012 22:40
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Python base-conversion method
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""" | |
Source: http://djangosnippets.org/snippets/1431/ | |
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' | |
) | |
base57 = BaseConverter( | |
'ABCDEFGHJKLMNPQRSTUVWXYZ23456789abcdefghijkmnopqrstuvwxyz' | |
# Base57 is essentially Base62, but with five characters removed | |
# (I, O, l, 1, 0) because they are often mistaken for one another. | |
) | |
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 |
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