Chris Angelico <ros...@gmail.com>: > On Sun, Aug 19, 2018 at 11:54 PM, Marko Rauhamaa <ma...@pacujo.net> wrote: >>> 3) Every invocation of method() has to execute the class body, which >>> takes time. >> >> That's what happens with every method invocation in Python regardless. > > No. You have to execute the *class body*. Every method invocation has > to execute a function body. Yours includes a class definition. > Remember: The 'class' statement is NOT a declaration. It is an > executable statement.
Sorry, I was being imprecise. Obviously, whenever you execute a def statement, you have to execute a def statement. Similarly, whenever you execute a class statement, you have to execute a class statement. And executing a class statement involves certain chores. Intantiating an object involves a different set of chores. And invoking a method involves yet another set of chores. Some of these chores are heavier, some of them are lighter. But where I have used Python, performance hasn't been a bottleneck. It it were, I'd choose different approaches of implementation. > Oh, even easier then. You don't need any of this locality. Which means > the inner class is buying you a whole lot of nothing. When I first ran into Java's anonymous inner classes, I wondered why they hadn't simply introduced anonymous functions. In fact, the whole debacle ended up in a schism where C# forked out of Java and introduced delegates, which are a neat concept and should have been there in C++ from the get-go. In their arms race both C# and Java finally introduced lambdas. But now I'm thinking the original Java approach (anonymous inner classes) is probably the most versatile of them all. A single function rarely captures behavior. That's the job of an object with its multiple methods. In in order to create an ad-hoc object in Python, you will need an ad-hoc class. > Hmm... so it's fine to create a class at run time, but it's not okay > to define its methods at run time. Yes. > I'm seriously confused here as to what you gain by that. How is it of > value to create a new class at run time, but to require that all its > methods and attributes be hand-written in the source code, and thus > completely fixed? Not completely fixed because the methods of the inner class can refer to the variables of the outer scope. Marko -- https://mail.python.org/mailman/listinfo/python-list
