Does Python have something like anonymous inner classes of Java?

Question

In Java you can define a new class inline using anonymous inner classes. This is useful when you need to rewrite only a single method of the class.

Suppose that you want create a subclass of OptionParser that overrides only a single method (for example exit()). In Java you can write something like this:

new OptionParser () {

    public void exit() {
        // body of the method
    }
};

This piece of code creates a anonymous class that extends OptionParser and override only the exit() method.

There is a similar idiom in Python? Which idiom is used in these circumstances?

Answer 1

You can use the type(name, bases, dict) builtin function to create classes on the fly. For example:

op = type("MyOptionParser", (OptionParser,object), {"foo": lambda self: "foo" })
op().foo()

Since OptionParser isn't a new-style class, you have to explicitly include object in the list of base classes.