class BankAccount:
    def __init__(self, aId, pin, balance = 100): # balance's default value is 100
        self._id      = aId
        self._pin     = pin
        self._balance = balance
    @property
    def id(self):
        return self._id
    @property
    def pin(self):
        return self._pin
    @property
    def balance(self):
        return self._balance

    @pin.setter
    def pin(self, newPin):
        self._pin = newPin

    @balance.setter
    def balance(self, newBal):
        self._balance = newBal

    def changePin(self, oldPin, newPin):
        if oldPin == self._pin:
            self._pin = newPin
            return True
        else:
            return False

    def deposit(self, amount):
        if amount > 0:              # Simple validation
            self._balance += amount
            return True
        else:
            return False

    def withdraw(self, amount):
        if amount > 0 and amount <= self._balance:
            self._balance -= amount
            return True
        else:
            return False

    def transfer(self, amount, tAccount):   # tAccount is the account to transfer
        if amount > 0 and amount <= self._balance:
            self._balance     -= amount
            tAccount._balance += amount     # Add amount to the other account
            return True
        else:
            return False

    def __str__(self):
        s = "Account: {}  Balance: {:.2f}".format(self._id, self._balance)
        return s