1.4 面向對象解決方案：初識類

代碼清單1-7展示了一種面向對象方法，該方法將一個賬戶的所有代碼和關聯數據組合到一起。這里有許多新概念，從下一章開始將詳細介紹所有細節。盡管你現在可能沒有完全理解這個示例，但是注意，這里把代碼和數據合并到一個腳本（稱為類）中。下面是你在本書中第一次接觸到的面向對象代碼。

代碼清單1-7：第1個Python類示例（文件: Account.py）

# Account class
　
class Account():
    def __init__(self, name, balance, password):
        self.name = name
        self.balance = int(balance)
        self.password = password
　
    def deposit(self, amountToDeposit, password):
        if password != self.password:
            print(‘Sorry, incorrect password’)
            return None
　
        if amountToDeposit < 0:
            print(‘You cannot deposit a negative amount’)
            return None
　
        self.balance = self.balance + amountToDeposit
        return self.balance
　
　
　
    def withdraw(self, amountToWithdraw, password):
        if password != self.password:
            print(‘Incorrect password for this account’)
            return None
　
        if amountToWithdraw < 0:
            print(‘You cannot withdraw a negative amount’)
            return None
　
        if amountToWithdraw > self.balance:
            print(‘You cannot withdraw more than you have in your account’)
            return None
　
        self.balance = self.balance - amountToWithdraw
        return self.balance
　
    def getBalance(self, password):
        if password != self.password:
            print(‘Sorry, incorrect password’)
            return None
        return self.balance
　
    # Added for debugging
    def show(self):
        print(‘       Name:’, self.name)
        print(‘       Balance:’, self.balance)
        print(‘       Password:’, self.password)
        print()

現在，思考這里的函數與前面的過程式編程示例有什么相似之處。函數的名稱與之前相同（show()、getBalance()、deposit()和withdraw()），但這里還有一些使用了self（或self.）的代碼。后面的章節將介紹它的含義。