convert integer to binary

[Dan Bishop]

Jan Olderdissen <jolderdissen at ixiacom.com> wrote in message news:<u8n5bvo6ks4lg757ujptg6i5v2v0gpsk08 at 4ax.com>...
> >I couldn't find any function in Python to convert integers to binary
> >and vice versa, for example:
> 
> Try int ("1111", 2) to go from binary to integer. For the reverse
> direction, you'll probably have to implement a couple of lines of
> actual code. :-)

I've implemented such a function in only one line before, but here's
the readable version, plus 3 related functions.

# ------------ baseconv.py ------------

from __future__ import division
import string, math

digits = string.digits + string.uppercase

def atoi(s, radix=10):
   "the integer represented by the string s in the given base"
   try:
      return int(s, radix)
   except OverflowError:
      return long(s, radix)

def atof(s, radix=10):
   "the float represented by the string s in the given base"
   if s[0] == '-':
      return -atof(s[1:], radix)
   decimalPointIndex = s.find('.')
   if decimalPointIndex < 0:
      return float(atoi(s, radix))
   iPart = atoi(s[:decimalPointIndex], radix)
   fPart = s[decimalPointIndex+1:]
   if fPart:
      fPart = atoi(fPart, radix) / radix ** len(fPart)
   else:
      fPart = 0
   return iPart + fPart

def itoa(num, radix=10):
   "the string representing the integer num in the given base"
   if num == 0:
      return '0'
   isNegative = num < 0
   if isNegative:
      num = -num
   d = []
   while num > 0:
      num, lastDigit = divmod(num, radix)
      d.append(digits[lastDigit])
   if isNegative:
      d.append('-')
   d.reverse()
   return ''.join(d)

def ftoa(num, radix=10):
   "the string representing the float num in the given base"
   if num < 0:
      return '-' + ftoa(num, radix)
   significantDigits = int(math.ceil(52 * math.log(2) /
math.log(radix)))
   leftDigits = int(math.log(num) / math.log(radix) + 1)
   decimalPlaces = max(significantDigits - leftDigits, 0)
   scaledNum = long(num * radix ** decimalPlaces + 0.5)
   iPart, fPart = divmod(scaledNum, radix ** decimalPlaces)
   iPart = itoa(iPart, radix)
   fPart = string.zfill(itoa(fPart, radix), decimalPlaces)
   s = "%s.%s" % (iPart, fPart)
   lastDigitPosition = len(s) - 1
   while s[lastDigitPosition] == digits[0]:
      lastDigitPosition -= 1
   return s[:lastDigitPosition+1]