[Python-Dev] PEP 3144 review. (original) (raw)

Terry Reedy tjreedy at udel.edu
Wed Sep 30 18:38:44 CEST 2009

Mark Dickinson wrote:

On Wed, Sep 30, 2009 at 1:44 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:

Please could someone who understands the uses of IPNetwork better than I do explain why the following wouldn't be a significant problem, if eq and hash were modified to disregard the .ip attribute as suggested:

linus = IPv4Network('172.16.200.1/24') snoopy = IPv4Network('172.16.200.3/24') fqdn = {linus: 'linus.peanuts.net', snoopy: 'snoopy.peanuts.net'} fqdn[linus] # expecting 'linus.peanuts.net' 'snoopy.peanuts.net' Is this just a problem of education, teaching the users not to abuse IPv4Network this way? Or is this just an unlikely use of IPv4Network? Or have I misunderstood the proposal altogether?

This gets at why I suggested the docs be organized as I suggested, with 'Network is range of addresses defined by address within range ...' and 'Definition address is retained' immediately followed by 'Definition address is mostly ignored, including for comparisons'. The latter caveat should mention the implication for hash() and set/dict membership. The point is to emphasize from the beginning that a network is a network (with an address, that many will ignore), rather than an address (with a network).

Terry Jan Reedy

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