[Tutor] Function for converting ints from base10 to base2?

[Dick Moores]

I was surprised to be unable to find a function in Python for 
converting ints from base10 to base2. Is there one?

I wrote one, but have I reinvented the wheel again? (Even if I have, 
it was an interesting exercise for me.)

I know some of you CS people won't like what I do with negative ints, 
but I wanted it this way. On other points than that, I'd appreciate 
criticism/suggestions.

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def computeBin(n):
     """converts base10 integer n to base2 b as string"""
     from math import log, floor
     sign = ''
     if n == 0:
         b = '0'
     else:
         if n < 0:
             sign = "-"
             n = -n
         e = int(floor(log(n,2)))
         b = '1'

         for x in range(e):
             r = n % 2**e
             if r >= 2**(e-1):
                 b += '1'
             else:
                 b += '0'
             e -= 1
     return sign + b

def printResult(n,b):
     print "%d is %s" % (n, b)

def confirmResult(n,b):
     print "Confirming using int():"
     print "int(%s,2) is %s" % (b, int(b,2))

if __name__ == '__main__':
     n = 1234567890
     b = computeBin(n)
     printResult(n,b)
     confirmResult(n,b)
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Dick Moores