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

Terry Carroll carroll at tjc.com
Thu Feb 22 02:17:27 CET 2007

On Tue, 20 Feb 2007, Dick Moores wrote:

> 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 like the approach of mapping hex or octal digits posted by Alan and Bob,
but, not thinking of that, this would be my straightforward approach:

def computeBin(n):
     """converts base10 integer n to base2 b as string"""
     if n == 0: return '0'
     sign = ['','-'][n<0]
     num = abs(n)
     seq = []
     while (num != 0):
         (num, bit) = divmod(num, 2)
     return ''.join(reversed(seq))

if __name__ == "__main__":
    x = 1234567890
    assert x == int(computeBin(x),2)
    x = -1234567890
    assert x == int(computeBin(x),2)

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