Introduction to Machine Learning

As I have just mentioned, everything is an object in Python.

Naturally, you can define your own classes. In Python 3, all classes inherit the object class by default.

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class Person:
    pass

person = Person()

Line 2: pass is a special statement in Python that basically says “do nothing”. Useful when you need to put something in an otherwise empty indented block.

Line 4: This creates an instance of Person (i.e. calling the constructor), and assigns the instance to the variable person.

This is equivalent to the following in C++.

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// C++ equivalent
class Person {};

int main() {
   Person* person = new Person();
   delete person;
   return 0;
}

Note that Python always creates object instances in the memory heap. So this is different from the static memory allocation version in C++ (Person person; or Person person(); or Person person = Person()).

I will discuss more about Object-Oriented Programming in Python later on. This page is just to ensure that you are clear about the syntax differences between C++ and Python for object constructors. We will be talking about objects a lot throughout this tutorial.

Again – I cannot stress this enough – remember that in Python, a variable does not have a type. It is what the variable is pointing to that has a type! This is key to understanding how to “think” of variables in Python compared to in C++. Just have the diagrams from the previous page constantly in your mind as we go along!