On Tuesday, May 20, 2014, Greg Ewing <greg.ew...@canterbury.ac.nz> wrote:
> Chris Barker wrote: > >> Personally, I often miss the ability to chain operations on mutable >> objects, but I can only imagine that that design decision was made for good >> reason. However, as I teach Python, I find I have nothing to say other than >> "that's the way it's done in Python". >> > > Python has better ways of doing many of the things that > method chaining is used for in other languages. In Java, > for example, I often see it used as a somewhat klunky > workaround for the lack of keyword arguments when > initialising objects. > > Other than that, it seems to be mainly for stuffing > multiple operations into one line, which is not something > the Python style generally goes in for. > > I suppose the argument could be that for mutable objects, returning None >> is an indicator that you are a) working with an mutable object, and b) that >> the method changes the internal state. But the .pop() example demonstrates >> that a method can both return something meaningful, and change internal >> state, so I'm not sure it's really a distinction worth making. >> > > It's not just about mutating the object, it's about a > mutating method with a name that could also plausibly > be the name of a non-mutating method. The canonical > example is sort(), which, if you didn't already know, > could equally well be mutating or non-mutating. In > those cases, I think it's worth making it difficult > to get wrong. This is the key reason, by far the most important. > This doesn't apply so much to pop(), which sounds > much more like a mutating method than a non-mutating > one, so it's less likely you'll make a mistake. > > -- > Greg > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: https://mail.python.org/mailman/options/python-dev/ > guido%40python.org > -- --Guido van Rossum (on iPad)
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