binary to decimal conversion

Moshe Zadka moshez at math.huji.ac.il
Sat Mar 18 23:35:16 CET 2000


On 18 Mar 2000, Michael Esveldt wrote:

> This morning I wrote a function that takes a binary number as a string 
> and converts it to an integer. There must be a way to optimize this 
> function, anyone have some tips?
> 
> def btoi(num):
>     output = 0
>     col = range(len(num))
>     col.reverse()
      current_power = 1
>     for bit in range(len(num)):
>         output = output + pow(2,col[bit])*int(num[bit])
Better:
          if num[bit] == '1':
              output = output+current_power
          current_power = current_power << 1

Or try some list functions:

powers = map(pow, [2]*len(num), range(len(num)))
return reduce(operator.add, map(operator.mult, powers, map(int, num)))

(You can calculate powers in advance, and just take slices)
--
Moshe Zadka <mzadka at geocities.com>. 
http://www.oreilly.com/news/prescod_0300.html
http://www.linux.org.il -- we put the penguin in .com





More information about the Python-list mailing list