```Nick Coghlan <ncogh...@gmail.com> added the comment:

I think the aspect that makes this potentially worthy of a helper function is
the need to dynamically adjust the field width based on whether you're printing
an IPv4 address or an IPv6 one, whether you're printing it in binary or
hexadecimal, whether you're printing separator characters, and whether you're
printing the base indicator prefix.```
```
For example, consider the following:

```
>>> ip4
>>> ip6
>>> format(int(ip4), "#041_b")
'0b0000_0001_0000_0010_0000_0011_0000_0100'
>>> format(int(ip6), "#041_x")
'0x0000_0000_0000_0000_0001_0002_0003_0004'
```

The "41" in those examples comes from "prefix_len + (num_bits / bits_per_char)
+ (num_bits / bits_per_char / chars_per_separator) - 1":

IPv4 in binary: 2 + (32 / 1) + (32 / 1 / 4) - 1 = 2 + 32 + 8 - 1 = 41
IPv6 in hex: 2 + (128 / 4) + (128 / 1 / 4) - 1 = 2 + 32 + 8 - 1 = 41

So I think the potentially interesting method to implement here would be
*__format__*, such that the field width calculation could be made implicit
based on the other options selected.

While backwards compatibility means that IP address formatting would still need
to be equivalent to "str(ip)" by default, it would be reasonably
straightforward to make "format(ip, 'b')" output the number in binary,
"format(ip, 'x')" do it in hex, and "format(ip, 'n')" be equivalent to "b" for
IPv4 addresses, and "x" for IPv6 ones.

Unlike ordinary numbers, the IP addresses would always be zero-padded to a
fixed width (32-bits for IPv4, 128 bits for IPv6), but "#" and "_" would be
accepted to indicate whether or to add the base indicator prefix and/or group
separators.

Given those enhancements, the display examples above would become:

```
>>> format(ip4, "#_n")
'0b0000_0001_0000_0010_0000_0011_0000_0100'
>>> format(ip6, "#_n")
'0x0000_0000_0000_0000_0001_0002_0003_0004'
```

----------

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```