Lab 6: OOP
2640字约9分钟
CS61ABerkeleyPython
2024-12-29
Starter Files
Download lab06.zip.
如果官方链接失效，你也可以通过我的 github 仓库 CS61A_Fall2024来获取我的代码。
提示
初始代码可以在 github 仓库历史 Commits 中的 Commits on Dec 29, 2024 的 initial lab06 找到
Required Questions
Object-Oriented Programming
Q1: Bank Account
扩展 BankAccount 类以包含 transactions 属性。此属性应为一个列表，用于跟踪账户上进行的每笔交易。每当调用 deposit 或 withdraw 方法时，都应创建一个新的 Transaction 实例并将其添加到列表中，即使操作未成功。
Transaction 类应具有以下属性：
before：交易前的账户余额。after：交易后的账户余额。id：交易 ID，即该账户上之前进行的交易（存款或取款）的数量。特定BankAccount实例的交易 ID 必须是唯一的，但此id不必在所有账户中都是唯一的。换句话说，您只需确保同一 BankAccount 进行的两个Transaction对象没有相同的id。
此外，Transaction 类应具有以下方法：
changed()：如果余额发生变化（即，before与after不同），则返回True，否则返回False。report()：返回描述交易的字符串。该字符串应以交易 ID 开头并描述余额的变化。查看 doctests 以了解预期输出。
class Transaction:
def __init__(self, id, before, after):
self.id = id
self.before = before
self.after = after
def changed(self):
"""Return whether the transaction resulted in a changed balance."""
"*** YOUR CODE HERE ***"
def report(self):
"""Return a string describing the transaction.
>>> Transaction(3, 20, 10).report()
'3: decreased 20->10'
>>> Transaction(4, 20, 50).report()
'4: increased 20->50'
>>> Transaction(5, 50, 50).report()
'5: no change'
"""
msg = 'no change'
if self.changed():
"*** YOUR CODE HERE ***"
return str(self.id) + ': ' + msg
class BankAccount:
"""A bank account that tracks its transaction history.
>>> a = BankAccount('Eric')
>>> a.deposit(100) # Transaction 0 for a
100
>>> b = BankAccount('Erica')
>>> a.withdraw(30) # Transaction 1 for a
70
>>> a.deposit(10) # Transaction 2 for a
80
>>> b.deposit(50) # Transaction 0 for b
50
>>> b.withdraw(10) # Transaction 1 for b
40
>>> a.withdraw(100) # Transaction 3 for a
'Insufficient funds'
>>> len(a.transactions)
4
>>> len([t for t in a.transactions if t.changed()])
3
>>> for t in a.transactions:
... print(t.report())
0: increased 0->100
1: decreased 100->70
2: increased 70->80
3: no change
>>> b.withdraw(100) # Transaction 2 for b
'Insufficient funds'
>>> b.withdraw(30) # Transaction 3 for b
10
>>> for t in b.transactions:
... print(t.report())
0: increased 0->50
1: decreased 50->40
2: no change
3: decreased 40->10
"""
# *** YOU NEED TO MAKE CHANGES IN SEVERAL PLACES IN THIS CLASS ***
def __init__(self, account_holder):
self.balance = 0
self.holder = account_holder
def deposit(self, amount):
"""Increase the account balance by amount, add the deposit
to the transaction history, and return the new balance.
"""
self.balance = self.balance + amount
return self.balance
def withdraw(self, amount):
"""Decrease the account balance by amount, add the withdraw
to the transaction history, and return the new balance.
"""
if amount > self.balance:
return 'Insufficient funds'
self.balance = self.balance - amount
return self.balance使用 Ok 来测试你的代码：
python ok -q BankAccount以下内容包含答案
class Transaction:
def __init__(self, id, before, after):
self.id = id
self.before = before
self.after = after
def changed(self):
"""Return whether the transaction resulted in a changed balance."""
"*** YOUR CODE HERE ***"
if self.before != self.after:
return True
else:
return False
def report(self):
"""Return a string describing the transaction.
>>> Transaction(3, 20, 10).report()
'3: decreased 20->10'
>>> Transaction(4, 20, 50).report()
'4: increased 20->50'
>>> Transaction(5, 50, 50).report()
'5: no change'
"""
msg = 'no change'
if self.changed():
"*** YOUR CODE HERE ***"
if self.before < self.after:
msg = f'increased {self.before}->{self.after}'
else:
msg = f'decreased {self.before}->{self.after}'
return str(self.id) + ': ' + msg
class BankAccount():
class BankAccount(Transaction):
"""A bank account that tracks its transaction history.
>>> a = BankAccount('Eric')
>>> a.deposit(100) # Transaction 0 for a
100
>>> b = BankAccount('Erica')
>>> a.withdraw(30) # Transaction 1 for a
70
>>> a.deposit(10) # Transaction 2 for a
80
>>> b.deposit(50) # Transaction 0 for b
50
>>> b.withdraw(10) # Transaction 1 for b
40
>>> a.withdraw(100) # Transaction 3 for a
'Insufficient funds'
>>> len(a.transactions)
4
>>> len([t for t in a.transactions if t.changed()])
3
>>> for t in a.transactions:
... print(t.report())
0: increased 0->100
1: decreased 100->70
2: increased 70->80
3: no change
>>> b.withdraw(100) # Transaction 2 for b
'Insufficient funds'
>>> b.withdraw(30) # Transaction 3 for b
10
>>> for t in b.transactions:
... print(t.report())
0: increased 0->50
1: decreased 50->40
2: no change
3: decreased 40->10
"""
# *** YOU NEED TO MAKE CHANGES IN SEVERAL PLACES IN THIS CLASS ***
def __init__(self, account_holder):
self.balance = 0
self.holder = account_holder
self.transactions = []
self.id = 0
def deposit(self, amount):
"""Increase the account balance by amount, add the deposit
to the transaction history, and return the new balance.
"""
self.transactions.append(Transaction(self.id, self.balance, self.balance + amount))
self.id += 1
self.balance = self.balance + amount
return self.balance
def withdraw(self, amount):
"""Decrease the account balance by amount, add the withdraw
to the transaction history, and return the new balance.
"""
if amount > self.balance:
self.transactions.append(Transaction(self.id, self.balance, self.balance))
self.id += 1
return 'Insufficient funds'
self.transactions.append(Transaction(self.id, self.balance, self.balance - amount))
self.id += 1
self.balance = self.balance - amount
return self.balanceQ2: Email
电子邮件系统有三个类：Email 、Server 和 Client 。Client 可以 compose 电子邮件，并将其 send 到 Server 。然后 Server 将其发送到另一个 Client 的 inbox 。为了实现这一点， Server 有一个名为 clients 的字典，它将 Client 的名称映射到 Client 实例。
假设客户端永远不会更改其使用的服务器，并且它只使用该服务器撰写电子邮件。
填写以下定义以完成实现！ Email 类已为您完成。
重要
在开始之前，请确保您阅读了整个代码片段以了解类之间的关系，并注意方法的参数类型。考虑一下您可以在每个方法中访问哪些变量，以及如何使用它们来访问其他类及其方法。
注意：
Email类中__init__(self, msg, sender, reception_name)方法中的sender参数是Client实例。Server类中register_client(self, client)方法的client参数是一个Client实例。Server类中send(self, email)方法的email参数是一个Email实例。
class Email:
"""An email has the following instance attributes:
msg (str): the contents of the message
sender (Client): the client that sent the email
recipient_name (str): the name of the recipient (another client)
"""
def __init__(self, msg, sender, recipient_name):
self.msg = msg
self.sender = sender
self.recipient_name = recipient_name
class Server:
"""Each Server has one instance attribute called clients that is a
dictionary from client names to client objects.
"""
def __init__(self):
self.clients = {}
def send(self, email):
"""Append the email to the inbox of the client it is addressed to.
email is an instance of the Email class.
"""
____.inbox.append(email)
def register_client(self, client):
"""Add a client to the clients mapping (which is a
dictionary from client names to client instances).
client is an instance of the Client class.
"""
____[____] = ____
class Client:
"""A client has a server, a name (str), and an inbox (list).
>>> s = Server()
>>> a = Client(s, 'Alice')
>>> b = Client(s, 'Bob')
>>> a.compose('Hello, World!', 'Bob')
>>> b.inbox[0].msg
'Hello, World!'
>>> a.compose('CS 61A Rocks!', 'Bob')
>>> len(b.inbox)
2
>>> b.inbox[1].msg
'CS 61A Rocks!'
>>> b.inbox[1].sender.name
'Alice'
"""
def __init__(self, server, name):
self.inbox = []
self.server = server
self.name = name
server.register_client(____)
def compose(self, message, recipient_name):
"""Send an email with the given message to the recipient."""
email = Email(message, ____, ____)
self.server.send(email)使用 Ok 来测试你的代码：
python ok -q Client以下内容包含答案
class Server:
"""Each Server has one instance attribute called clients that is a
dictionary from client names to client objects.
"""
def __init__(self):
self.clients = {}
def send(self, email):
"""Append the email to the inbox of the client it is addressed to.
email is an instance of the Email class.
"""
____.inbox.append(email)
self.clients[email.recipient_name].inbox.append(email)
def register_client(self, client):
"""Add a client to the clients mapping (which is a
dictionary from client names to client instances).
client is an instance of the Client class.
"""
____[____] = ____
self.clients[client.name] = client
class Client:
"""A client has a server, a name (str), and an inbox (list).
>>> s = Server()
>>> a = Client(s, 'Alice')
>>> b = Client(s, 'Bob')
>>> a.compose('Hello, World!', 'Bob')
>>> b.inbox[0].msg
'Hello, World!'
>>> a.compose('CS 61A Rocks!', 'Bob')
>>> len(b.inbox)
2
>>> b.inbox[1].msg
'CS 61A Rocks!'
>>> b.inbox[1].sender.name
'Alice'
"""
def __init__(self, server, name):
self.inbox = []
self.server = server
self.name = name
server.register_client(____)
server.register_client(self)
def compose(self, message, recipient_name):
"""Send an email with the given message to the recipient."""
email = Email(message, ____, ____)
email = Email(message, self, recipient_name)
self.server.send(email)Q3: Mint
铸币厂是铸造硬币的地方。在这个问题中，您将实现一个可以输出具有正确年份和价值的 Coin 的 Mint 类。
- 每个
Mint实例都有一个year。update方法将实例的year设置为Mint类的present_year类属性。 create方法采用Coin的子类（不是实例！），然后创建并返回该子类的一个实例，该实例带有Mint的年份戳（如果未更新，则可能与Mint.present_year不同。）Coin的worth方法返回硬币的cents价值，加上超过 50 年的每个年份的额外一分。可以通过从Mint类的present_year类属性中减去硬币的年份来确定硬币的年龄。
class Mint:
"""A mint creates coins by stamping on years.
The update method sets the mint's stamp to Mint.present_year.
>>> mint = Mint()
>>> mint.year
2024
>>> dime = mint.create(Dime)
>>> dime.year
2024
>>> Mint.present_year = 2104 # Time passes
>>> nickel = mint.create(Nickel)
>>> nickel.year # The mint has not updated its stamp yet
2024
>>> nickel.worth() # 5 cents + (80 - 50 years)
35
>>> mint.update() # The mint's year is updated to 2104
>>> Mint.present_year = 2179 # More time passes
>>> mint.create(Dime).worth() # 10 cents + (75 - 50 years)
35
>>> Mint().create(Dime).worth() # A new mint has the current year
10
>>> dime.worth() # 10 cents + (155 - 50 years)
115
>>> Dime.cents = 20 # Upgrade all dimes!
>>> dime.worth() # 20 cents + (155 - 50 years)
125
"""
present_year = 2024
def __init__(self):
self.update()
def create(self, coin):
"*** YOUR CODE HERE ***"
def update(self):
"*** YOUR CODE HERE ***"
class Coin:
cents = None # will be provided by subclasses, but not by Coin itself
def __init__(self, year):
self.year = year
def worth(self):
"*** YOUR CODE HERE ***"
class Nickel(Coin):
cents = 5
class Dime(Coin):
cents = 10使用 Ok 来测试你的代码：
python ok -q Mint以下内容包含答案
class Mint:
"""A mint creates coins by stamping on years.
The update method sets the mint's stamp to Mint.present_year.
>>> mint = Mint()
>>> mint.year
2024
>>> dime = mint.create(Dime)
>>> dime.year
2024
>>> Mint.present_year = 2104 # Time passes
>>> nickel = mint.create(Nickel)
>>> nickel.year # The mint has not updated its stamp yet
2024
>>> nickel.worth() # 5 cents + (80 - 50 years)
35
>>> mint.update() # The mint's year is updated to 2104
>>> Mint.present_year = 2179 # More time passes
>>> mint.create(Dime).worth() # 10 cents + (75 - 50 years)
35
>>> Mint().create(Dime).worth() # A new mint has the current year
10
>>> dime.worth() # 10 cents + (155 - 50 years)
115
>>> Dime.cents = 20 # Upgrade all dimes!
>>> dime.worth() # 20 cents + (155 - 50 years)
125
"""
present_year = 2024
def __init__(self):
self.update()
def create(self, coin):
"*** YOUR CODE HERE ***"
if coin == Dime:
return Dime(self.year)
else:
return Nickel(self.year)
def update(self):
"*** YOUR CODE HERE ***"
self.year = self.present_year
class Coin:
cents = None # will be provided by subclasses, but not by Coin itself
def __init__(self, year):
self.year = year
def worth(self):
"*** YOUR CODE HERE ***"
return self.cents + max(Mint.present_year - self.year - 50, 0)
class Nickel(Coin):
cents = 5
class Dime(Coin):
cents = 10Check Your Score Locally
您可以通过运行
python3 ok --score在本地检查此作业每个问题的得分
这不会提交作业！当您对分数满意时，请将作业提交给 Gradescope 以获得学分。
PS D:\Github\CS61A_Fall2024\lab\lab06> python ok --score
=====================================================================
Assignment: Lab 6
OK, version v1.18.1
=====================================================================
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Scoring tests
---------------------------------------------------------------------
Doctests for BankAccount
>>> from lab06 import *
>>> a = BankAccount('Eric')
>>> a.deposit(100) # Transaction 0 for a
100
>>> b = BankAccount('Erica')
>>> a.withdraw(30) # Transaction 1 for a
70
>>> a.deposit(10) # Transaction 2 for a
80
>>> b.deposit(50) # Transaction 0 for b
50
>>> b.withdraw(10) # Transaction 1 for b
40
>>> a.withdraw(100) # Transaction 3 for a
'Insufficient funds'
>>> len(a.transactions)
4
>>> len([t for t in a.transactions if t.changed()])
3
>>> for t in a.transactions:
... print(t.report())
0: increased 0->100
1: decreased 100->70
2: increased 70->80
3: no change
>>> b.withdraw(100) # Transaction 2 for b
'Insufficient funds'
>>> b.withdraw(30) # Transaction 3 for b
10
>>> for t in b.transactions:
... print(t.report())
0: increased 0->50
1: decreased 50->40
2: no change
3: decreased 40->10
Score: 1.0/1
---------------------------------------------------------------------
Doctests for Client
>>> from lab06 import *
>>> s = Server()
>>> a = Client(s, 'Alice')
>>> b = Client(s, 'Bob')
>>> a.compose('Hello, World!', 'Bob')
>>> b.inbox[0].msg
'Hello, World!'
>>> a.compose('CS 61A Rocks!', 'Bob')
>>> len(b.inbox)
2
>>> b.inbox[1].msg
'CS 61A Rocks!'
>>> b.inbox[1].sender.name
'Alice'
Score: 1.0/1
---------------------------------------------------------------------
Doctests for Mint
>>> from lab06 import *
>>> mint = Mint()
>>> mint.year
2024
>>> dime = mint.create(Dime)
>>> dime.year
2024
>>> Mint.present_year = 2104 # Time passes
>>> nickel = mint.create(Nickel)
>>> nickel.year # The mint has not updated its stamp yet
2024
>>> nickel.worth() # 5 cents + (80 - 50 years)
35
>>> mint.update() # The mint's year is updated to 2104
>>> Mint.present_year = 2179 # More time passes
>>> mint.create(Dime).worth() # 10 cents + (75 - 50 years)
35
>>> Mint().create(Dime).worth() # A new mint has the current year
10
>>> dime.worth() # 10 cents + (155 - 50 years)
115
>>> Dime.cents = 20 # Upgrade all dimes!
>>> dime.worth() # 20 cents + (155 - 50 years)
125
Score: 1.0/1
---------------------------------------------------------------------
Point breakdown
BankAccount: 1.0/1
Client: 1.0/1
Mint: 1.0/1
Score:
Total: 3.0
Backup... 100% complete
Backup past deadline by 78 days, 1 hour, 33 minutes, and 27 seconds
Backup successful for user: zhiyong947@gmail.com
URL: https://okpy.org/cal/cs61a/fa24/lab06/backups/9O6W7J
OK is up to date
PS D:\Github\CS61A_Fall2024\lab\lab06>