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 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/archive%40mail-archive.com
