[Python-Dev] PEP 3144 review.

[Andrew McNamara]

>>> I don't see any valid reason for entering a network as "192.168.1.1/24"
>>> rather than the canonical "192.168.1.0/24". The former might indicate a
>>> typing error or a mental slip, so let's be helpful and signal it to the
>>> user.
>>
>> Or perhaps there can be an optional "strict=True" (or "strict=False")
>> argument to the constructor / parsing function.
>
>I can live w/ a default of strict=False.  there are plenty of cases
>where it's not an error and easy enough ways to check, if the
>developer is concerned, with or without an option.  eg if addr.ip !=
>addr.network:

I agree - there are definitely times when it is not an error, but I don't
like the idea of a "strict" flag.

I've done a bit of everything - router configs with a national ISP,
scripts to manage host configuration, user interfaces, you name it.
The way I see it, we need:

 * Two address classes that describe a single IP end-point - "Address" with
   no mask and "AddressWithMask" (the later being the current Network
   class, minus the container-like behaviour).

 * A "Network" container-like class. Same as the current Network class,
   but addresses with masked bits would be considered an error.

This is along the lines that RDM was suggesting, except that we remove the
container behaviour from AddressWithMask.

Additionally:

 * The .network attribute on an AddressWithMask would return a Network
   instance.

 * An Address class would not have a .network attribute

 * Network.__contains__() would accept Network, Address and
   AddressWithMask. Only Network implements __contains__ -
   an AddressWithMask can't contain another address, although it's
   .network can.

 * Maybe an Address should compare equal with an AddressWithMask if
   the address is identical and the mask is equivalent to /32?

Personally, I don't see a strong use-case for the list-like indexing and
iteration behaviour - I think it's enough to implement some basic
container behaviour, but I won't object to the iterator and indexing,
provided they don't distort the rest of the design (which I fear they
are doing now). Iterating or indexing a network should return Address
or AddressWithMask instances - if the later, the mask should match the
parent network's mask.

I'm not particularly wedded to the name "AddressWithMask" - maybe it
could be NetworkAddress or MaskedAddress or ?

-- 
Andrew McNamara, Senior Developer, Object Craft
http://www.object-craft.com.au/