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Integer to "binary string"?

Dan Bishop danb_83 at yahoo.com
Mon Dec 16 22:43:13 EST 2002 
Alfred Morgan <amorgan at netlojix.com> wrote in message news:<3DFE6179.4030601 at netlojix.com>...
> I decided to write a version 2 of my bin function.  Since version 1 
> couldn't handle negative numbers I added an assertion otherwise it would 
> get stuck in an infinite loop.  I also changed the way s added a '0' or 
> '1' since Dan didn't like my "short-circuiting" and/or method.
> I like it this way much better anyway because it's more petite.

Your code wasn't *that* bad; I just didn't feel like explaining it ;-)

I still wish Python had a real ?: operator, though.

> def bin(i):
>      assert i >= 0, "Can't be used for negative numbers."
>      s = ''
>      while i:
>          s = '01'[i & 1] + s
>          i >>= 1
>      return s or '0'

Or you could make it a special case of a generalized base conversion function:

# Can anyone write this in fewer lines?
def intToStr(num, radix=10):
   if num < 0: return '-' + intToStr(-num, radix)
   if num < radix: return "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[num]
   return intToStr(num // radix) + intToStr(num % radix)

def bin(num):
   return intToStr(num, 2)
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