[Tutor] Unexpected results with obj.method().method()

[C M Caine]

Thanks for the advice. As is often the case with these things, eryksun
pointed out a stupid mistake I'd made (mutating part of an immutable class)
that I should have seen.


On 6 December 2012 00:50, Oscar Benjamin <oscar.j.benjamin at gmail.com> wrote:

> On 5 December 2012 18:11, C M Caine <cmcaine at googlemail.com> wrote:
> > Dear all,
> >
> > I've written a class State that subclasses tuple. The class has a method
> > move_state that takes a move and returns a new state object representing
> the
> > new state of the game.
> >
> > I would expect S1 and S3 to be equal on the last line here, but they are
> > not.
> >
> >>>> import game
> >>>> S = game.State()
> >>>> S1 = S.move_state(1).move_state("SWAP")
> >>>> S2 = S.move_state(1)
> >>>> S3 = S2.move_state("SWAP")
> >>>> S1 == S3
> > False
> >
> > Printing the two states shows that they have very different internal
> states.
> >
> >>>> print S1
> >  (8, 8, 8, 8, 8, 8, 0)
> > 1                     0
> >  (7, 7, 7, 7, 7, 7, 7)
> >>>> print S3
> >  (7, 7, 7, 7, 7, 7, 7)
> > 0                     1
> >  (0, 8, 8, 8, 8, 8, 8)
>
> From your description above I have very little idea what you're trying
> to do. You have specified what you were expecting to happen why you're
> not happy with what actually happened, which is good. I still don't
> understand the problem, though. What is the *relevant* code that
> didn't do what you expected?
>
> > If anyone is interested, State represents the state of a 7 7 Kalah board.
>
> I don't know what a Kalah board is.
>
> > The full code is on pastebin http://pastebin.com/tUh0W5Se
>
> You were right not to post this code directly in your email as it's
> too big. For the same reason, though, I'm not prepared to read it
> through and try to understand the problem.
>
> It would be better if you could trim your problem down to a short
> example so that you can then post the full example. An important side
> effect of this process is that you will often discover the cause of
> the problem yourself before completing your email to the list.
>
> > Are my expectations faulty? (I hope not)
> > Have I made some mistake in my code to get these results?
>
> Probably at least one of the above is true, but I can't say much more
> than that. Have a read of http://sscce.org/ for some advice about how
> to post problems to a mailing list. If you follow the advice there you
> will find that
> 1) You will often be able to solve your problem yourself.
> 2) If you do post your problem to a mailing list you will be more
> likely to get a helpful response.
>
>
> Oscar
>
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