Python 2 to 3 Conversion

[Chris Angelico]

On Sun, Feb 18, 2018 at 4:35 AM, Wildman via Python-list
<python-list at python.org> wrote:
> Thanks to Chris and Ben.  Your suggestions were slightly
> different but both worked equally well, although I don't
> understand how that can be so.
>
>> struct.pack('256s', ifname[:15].encode('ascii'))
>> struct.pack('256s', ifname.encode('ascii'))

Those two will be identical for short interface names, but the first
form will truncate a longer name before encoding. I don't know what
the ioctl will do with a really long ifname, so it's probably worth
hanging onto the [:15] slicing.

> I was looking for a reliable way to determine the IP addy
> for a given network adapter.  That is what the code does
> but I don't understand how it does it either.
>
> Thanks again.  I will continue to research and study the
> code in the hope I will understand it.

Ah, makes sense. I'd probably do something like this:

>>> import socket
>>> s = socket.socket(type=socket.SOCK_DGRAM)
>>> s.connect(("8.8.8.8", 53))
>>> s.getsockname()[0]
'192.168.0.19'

But that's only going to show one (uplink) address. If I needed to get
ALL addresses for ALL network adapters, I'd either look for a library,
and if one wasn't easily found, I'd shell out to the "ip" command and
parse its output. :)

ChrisA