On Fri, Nov 11, 2011 at 10:23 AM, Jonathan <tart...@tartley.com> wrote:
> That's good to know René, but I *think* it's orthogonal to the question. > Please correct me if I'm wrong. > > If PyPy returns items in a different order than CPython, that doesn't > matter to me, so long as every invocation of my function in a particular > process ends up receiving a particular order, that doesn't change until > the process ends (or the cache is cleared.) > > The dict subclass is a great idea - but if the change in order isn't ever > manifested by a regular dict, then it implies to me that the 'sorted' call > isn't actually required in real life, so the need for this whole test > disappears. > > See also my imminent reply to Ross. > > Jonathan > > > Just because your code works Now, does not mean it will work in the future. Especially when the ordering is explicitly marked as a non-deterministic implementation detail. Relying on it to be deterministic when it is stated to be non-deterministic will mean that in the future you could get a failure. Relying on implementation quirks is fine, but not reliable. In your case though, the worst that can happen now is a cache miss. In the future though, your cache could be completely useless because every time the data could be in a different order. Testing on multiple platforms allows you to sometimes see a failure condition, which lets you test it. Likewise, using a randomised dict subclass will let you test your code as if there is an error condition. cya. ps. my randomised items subclass is buggy... I forgot that random.shuffle works in place, and doesn't return a shuffled sequence.
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