Inverse of int(s, base)?

[Dan Bishop]

olli at secnetix.de wrote in message news:<2gac73Fk1ooU1 at uni-berlin.de>...
> Hi,
> 
> Is there an inverse function of int(s, base) where base
> can be any number up to 36?

Yes, but for some reason it's not in the Python standard library.

...

> PS:  This is what I'm using right now.
> 
> import string
> str_digits = string.digits + string.ascii_lowercase
> 
> def str_base (x, base):
>         result = ""
>         while x:
>                 result = str_digits[x % base] + result
>                 x /= base

The above line should be "x //= base", so it works under -Qnew.

>         return result or "0"

That works (for positive integers), but it might be more efficient to
not create a new string each time through the loop.  An alternative
is:

def str_base(n, base=10):
   if n == 0:
      return '0'
   isNegative = n < 0
   if isNegative:
      n = -n
   result = []
   while n > 0:
      n, lastDigit = divmod(n, base)
      result.append(str_digits[lastDigit])
   if isNegative:
      result.append('-')
   result.reverse()
   return ''.join(result)