Conversion from IP string to integer, and backward in Python

Question

i have a little problem with my script, where i need to convert ip in form \'xxx.xxx.xxx.xxx\' to integer representation and go back from this form.

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Answer 1

My approach is to straightforwardly look at the the number the way it is stored, rather than displayed, and to manipulate it from the display format to the stored format and vice versa.

So, from an IP address to an int:

def convertIpToInt(ip):
    return sum([int(ipField) << 8*index for index, ipField in enumerate(reversed(ip.split('.')))])

This evaluates each field, and shifts it to its correct offset, and then sums them all up, neatly converting the IP address' display into its numerical value.

In the opposite direction, from an int to an IP address:

def convertIntToIp(ipInt):
    return '.'.join([str(int(ipHexField, 16)) for ipHexField in (map(''.join, zip(*[iter(str(hex(ipInt))[2:].zfill(8))]*2)))])

The numerical representation is first converted into its hexadecimal string representation, which can be manipulated as a sequence, making it easier to break up. Then, pairs are extracted by mapping ''.join onto tuples of pairs provided by zipping a list of two references to an iterator of the IP string (see How does zip(*[iter(s)]*n) work?), and those pairs are in turn converted from hex string representations to int string representations, and joined by '.'.