4J

Sometimes you may require to convert between base systems, for example from Octal to BASE10, as may be required when you use the os.mkdir or os.makedirs functions.

Here is a simple script demonstrating a possible implementation:

---

#!/usr/bin/python

BASE2 = "01"
BASE8 = "01234567"
BASE10 = "0123456789"
BASE16 = "0123456789ABCDEF"
BASE62 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz"

def baseconvert(number,fromdigits,todigits):

 """ converts a "number" between two bases of arbitrary digits

 The input number is assumed to be a string of digits from the
 fromdigits string (which is in order of smallest to largest
 digit). The return value is a string of elements from todigits
 (ordered in the same way). The input and output bases are
 determined from the lengths of the digit strings. Negative
 signs are passed through.

 decimal to binary
    baseconvert(555,BASE10,BASE2)
 '1000101011'

 binary to decimal
    baseconvert('1000101011',BASE2,BASE10)
 '555'

 integer interpreted as binary and converted to decimal (!)
    baseconvert(1000101011,BASE2,BASE10)
 '555'

 base10 to base4
    baseconvert(99,BASE10,"0123")
 '1203'

 base4 to base5 (with alphabetic digits)
    baseconvert(1203,"0123","abcde")
 'dee'

 base5, alpha digits back to base 10
    baseconvert('dee',"abcde",BASE10)
 '99'

 decimal to a base that uses A-Z0-9a-z for its digits
    baseconvert(257938572394L,BASE10,BASE62)
 'E78Lxik'

 ..convert back
    baseconvert('E78Lxik',BASE62,BASE10)
 '257938572394'

 binary to a base with words for digits (the function cannot convert this back)
    baseconvert('1101',BASE2,('Zero','One'))
 'OneOneZeroOne'

 """

 if str(number)[0]=='-':
  number = str(number)[1:]

  neg=1
 else:
  neg=0

 # make an integer out of the number

 x=long(0)
 for digit in str(number):

  x = x*len(fromdigits) + fromdigits.index(digit)

 
 # create the result in base 'len(todigits)'
 res=""
 while x > 0:
  digit = x % len(todigits)

  res = todigits[digit] + res
  x /= len(todigits)

 if neg:
  res = "-"+res

 return res

print "'700' octal (base8) is '" + str( baseconvert( 700, BASE8 ,BASE10 ) ) + "' in base10"

---

If you now want to make a directory with a create mode of 700 (octal) you will call

os.makedirs( "/tmp/test/path", baseconvert( 700, BASE8 ,BASE10 ) )

Until next time then... Need to get back to some coding :-)