Attributes
Let us now look at how you declare and initialise instance attributes (or instance variables), as well as use it.
In Java, you declare instance variables directly in the class declaration.
In Python, you dynamically attach new instance variables to the self object inside __init__() (Remember that self has only been allocated some space in memory at this point). This is where you initialise any attributes and their values (Lines 3-6).
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class Person:
def __init__(self, firstname, lastname, age=0):
self.firstname = firstname
self.lastname = lastname
self.age = age
self.friends = []
person = Person("Josiah", "Wang", 20) # What do you mean I don't look 20? :D
print(person.firstname)
print(person.lastname)
person.age = person.age + 1
print(person.age)
Like a normal function, you may assign default values for any of the arguments (e.g. age=0 in Line 2)
Accessing/updating the value of the attributes is just like in Java, with a dot (.) operator (Lines 9-13)
The attributes are public by default. What about private attributes? Hold that thought, we’ll come to that later!