面向对象

类的定义方法

class Account:
        def __init__(self, account_holder):
        #必须有`__init__`函数，该函数无需return
            self.balance = 0
            self.holder = account_holder
        def deposit(self, amount):
            self.balance = self.balance + amount
            return self.balance
        def withdraw(self, amount):
            if amount > self.balance:
                return 'Insufficient funds'
            self.balance = self.balance - amount
            return self.balance

子类的定义

class CheckingAccount(Account):
        """A bank account that charges for withdrawals."""
        withdraw_charge = 1
        interest = 0.01
        def withdraw(self, amount):
            return Account.withdraw(self, amount + self.withdraw_charge)


class SavingsAccount(Account):
        deposit_charge = 2
        def deposit(self, amount):
            return Account.deposit(self, amount - self.deposit_charge) 

多重继承

python允许多重继承。

class AsSeenOnTVAccount(CheckingAccount, SavingsAccount):
        def __init__(self, account_holder):
            self.holder = account_holder
            self.balance = 1

多重继承示意图