Question

I have worked in low level C programming for years and I don’t have enough exposure to Object oriented approaches. In C if I was developing some layered architecture then each layer has interfaces defined by function pointers. The advantage of that the whole layer can be replaced by just setting those function pointers at initialization to another layer.

I want the same thing but this time in Python. What is the coolest way to achieve that. To give a little background to my problem, I have a data generator which can output records to different mediums. The medium is specified at the configuration time. I don’t want to use if or switch statements here. The best way was to use function pointers in C but what are the options available here in Python. Any Object oriented approaches are also appreciated.

Thanks

Answer 1

Python supports functions as a first-class data type. So you can do something like:

def foo(x):
    print("foo: " + x)

def bar(x):
    print("bar: " + x)

f = foo
f("one")
f = bar
f("ten")

prints

foo: one
bar: ten

This is very similar to your experience with function pointers in C. Although Python certainly supports more elaborate object-oriented programming styles, you are under no obligation to use them.

An example using classes, where you can group related functions together:

class Dog:
    def noise(self, x):
        print("bark! " + x)
    def sleep(self):
        print("sleeping on floor")

class Cat:
    def noise(self, x):
        print("meow! " + x)
    def sleep(self):
        print("sleeping on keyboard")

a = Dog()
a.noise("hungry")
a.sleep()

a = Cat()
a.noise("hungry")
a.sleep()

This version prints:

bark! hungry
sleeping on floor
meow! hungry
sleeping on keyboard