[Tutor] Convert an IP address from binary to decimal

[Christian Witts]

On 18/01/2011 14:45, Tom Lin wrote:
> Hi guys,
>
> Please help me with this:
> Convert an IP address from binary string to decimal format.There are
> some preconditions:
> 1.IP address is in the form of '000010010....001100'.32 bits with no dot.
> 2.int(string, base) is not allowed, You have to implement the conversion .
> 3.Performance should be considered.
>
> For example an IP address like '11111111111111111111111111111111 '
> would be converted to '255.255.255.255'
>
> That's how I implement it. But I think it looks ugly and I wonder if
> there is a better way to do this.
>
> import re
> import sys
>
> def convert(bin_ip):
> patt = re.compile(r'\d{8}')
> bin_list = patt.findall(str(bin_ip))
>
> dec_list = []
> for bin in bin_list:
> sum = 0
> i = 7
> for n in bin:
> if int(n):
> sum = sum + 2**i
> i = i - 1
> dec_list.append(str(sum))
>
> dec_ip = '.'.join(dec_list)
> print dec_ip
>
> if __name__ == '__main__':
> bin_ip = sys.argv[1:]
> convert(bin_ip)
>
>
> Thanks in advance and excuse my poor English.
>
>
> Best regards,
> Tom
>
>
> _______________________________________________
> Tutor maillist  -  Tutor at python.org
> To unsubscribe or change subscription options:
> http://mail.python.org/mailman/listinfo/tutor
>   

If I knew the input to be perfect it would be a simple matter
'.'.join((str(int(input_ip[x:x+8], 2)) for x in range(4)))

-- 
Kind Regards,
Christian Witts