[Tutor] Convert an IP address from binary to decimal

[Tom Lin]

于 2011-1-18 21:08, Christian Witts 写道:
> 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
>>
>>
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> 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)))
>
Thanks, Chris. Your code looks pretty simple. Awesome!
But one precondition is not to use int(string, base). How would you
implement the conversion?