3、创建一个名为"BankAccount"的类，该类包含私有属性"accountNumber"和"balance"， 以及公有方法"getAccountNumber"、"getBalance"、"deposit"和"withdraw"来获取和操作私有属性的值。 在类的外部创建一个"BankAccount"对象并进行一些存款和取款操作，然后打印账户号码和余额。

下面是实现该题目的代码：

class BankAccount:
    def __init__(self, accountNumber, balance):
        self.__accountNumber = accountNumber
        self.__balance = balance

    def getAccountNumber(self):
        return self.__accountNumber

    def getBalance(self):
        return self.__balance

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

    def withdraw(self, amount):
        if amount <= self.__balance:
            self.__balance -= amount
        else:
            print("Insufficient balance!")

# 创建一个BankAccount对象
account = BankAccount("123456789", 1000)

# 存款和取款操作
account.deposit(500)
account.withdraw(200)

# 打印账户号码和余额
print("Account Number:", account.getAccountNumber())
print("Balance:", account.getBalance())

输出结果为：

Account Number: 123456789
Balance: 1300