There are many method names which have special significance in Python classes. The __init__ method is run as soon as an object of a class is instantiated (i.e. created). The method is useful to do any initialization (i.e. passing initial values to your object) you want to do with your object. One important conclusion that can be drawn from the information so far is that, __init__ is not a constructor. Many naive Python programmers get confused with it since __init__ gets called when we create an object. A closer inspection will reveal that the first parameter in __init__ is the object itself (object already exists). The function __init__ is called immediately after the object is created and is used to initialize it.

Here, we define the __init__ method as taking a parameter name (along with the usual self). Here, we just create a new field also called name. Notice these are two different variables even though they are both called 'name'. There is no problem because the dotted notation self.name means that there is something called "name" that is part of the object called "self" and the other name is a local variable. Since we explicitly indicate which name we are referring to, there is no confusion.

When creating new instance p, of the class Person, we do so by using the class name, followed by the arguments in the parentheses: p = Person('River Song').

We do not explicitly call the __init__ method. This is the special significance of this method.

Now, we are able to use the self.name field in our methods which is demonstrated in the say_himethod.

Multiple __init__ Methods

Now we are going to create a Point class with the following functionality:

There are two __init__ methods in the class definition. One initializes Point to a default value. The other initializes it to a custom location.

(This is also is a less trivial example.)

So here we created 3 points and gave them different values based on different ways we can initialize them.