Graph library for Python (was: Re: python bijection)

[geremy condra]

On Mon, Dec 7, 2009 at 5:48 PM, Steven D'Aprano
<steve at remove-this-cybersource.com.au> wrote:
> On Mon, 07 Dec 2009 17:23:24 -0500, geremy condra wrote:
>
>
>>>  * Graph.__iter__ could be mapped to an iterator using
>>>   the fastest traversal method for the graph nodes (ie. order does not
>>>   matter, it's only important that all nodes are found as fast as
>>>   possible)
>>
>> Again, it seems ambiguous as to whether nodes or edges are the intended
>> target here, and while the API can obviously dictate that, it seems a
>> bit like a case of "in the face of ambiguity, refuse the temptation to
>> guess" to me.
>
> Consider dicts. They have methods that iterates over keys, values, and
> (key, value) pairs, but if you just iterate over the dict itself, you get
> the keys. This was a deliberate design decision.
>
> It's not a matter of guessing in the face of ambiguity, but giving an
> easy way to get the most common case. Assuming that iteration over nodes
> is more common than iteration over edges, then iter(graph) should yield
> nodes in some unspecified order. If you need the nodes in a particular
> order, then you will call some method that guarantees the order, and if
> you want the edges, you call a method that gives edges.
>
> If you're not sure whether wanting nodes or edges will be more common,
> then you should wait until you, or the community, has more real-world
> experience with the module. Python had dicts for something approaching a
> decade before they became directly iterable.

I don't have a problem with adding this if there's a strong desire for it,
but at the moment I'm leaning towards a wait-and-see approach, for
all the reasons you described.

Geremy Condra