So here is a simple example of how to use classes: Suppose you are a finance institute. You want your customer's accounts to be managed by a computer. So you need to model those accounts. That is where classes come in. Working with classes is called object oriented programming. With classes you model real world objects in your computer. So, what do we need to model a simple bank account? We need a variable that saves the balance and one that saves the customers name. Additionally, some methods to in- and decrease the balance. That could look like:
class bankaccount():
def __init__(self, name, money):
self.name = name
self.money = money
def earn_money(self, amount):
self.money += amount
def withdraw_money(self, amount):
self.money -= amount
def show_balance(self):
print self.money
Now you have an abstract model of a simple account and its mechanism.
The def __init__(self, name, money) is the classes' constructor. It builds up the object in memory. If you now want to open a new account you have to make an instance of your class. In order to do that, you have to call the constructor and pass the needed parameters. In Python a constructor is called by the classes's name:
spidermans_account = bankaccount("SpiderMan", 1000)
If Spiderman wants to buy M.J. a new ring he has to withdraw some money. He would call the withdraw method on his account:
spidermans_account.withdraw_money(100)
If he wants to see the balance he calls:
spidermans_account.show_balance()
The whole thing about classes is to model objects, their attributes and mechanisms. To create an object, instantiate it like in the example. Values are passed to classes with getter and setter methods like `earn_money()ยด. Those methods access your objects variables. If you want your class to store another object you have to define a variable for that object in the constructor.