A class with methods in Python

The anatomy of a class: state in __init__, behavior in methods.

class BankAccount:
    def __init__(self, owner, balance=0):
        self.owner = owner
        self.balance = balance

    def deposit(self, amount):
        self.balance += amount

    def withdraw(self, amount):
        if amount > self.balance:
            raise ValueError("insufficient funds")
        self.balance -= amount


account = BankAccount("ada", 100)
account.deposit(50)
account.withdraw(30)

How it works

1. __init__ stores owner and balance on self.
2. deposit and withdraw mutate that state.
3. Invalid withdrawals raise instead of going negative.

Keywords and builtins used here

• BankAccount
• class
• def
• deposit
• if
• raise
• self
• withdraw

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Step 1 of 5 in Classes, step 39 of 72 in Language basics.

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