Homework 8
Due at 11:59:59 pm on Friday, 4/9/2021.
Instructions
Download hw08.zip. Inside the archive, you will find starter files for the questions in this homework, along with a copy of the OK autograder.
Submission: When you are done, submit with python3 ok --submit. You may submit more than once before the deadline; only the final submission will be scored. Check that you have successfully submitted your code on okpy.org. See this article for more instructions on okpy and submitting assignments.
Readings: This homework relies on following references:
OOP
Question 1: Person
Modify the following Person class to add a repeat method, which
repeats the last thing said. If nothing has been said yet, you can
have repeat return a string of your choosing. See the doctests for
an example of its use.
Hint: you will have to modify other methods as well, not just the
repeatmethod.
class Person(object):
"""Person class.
>>> steven = Person("Steven")
>>> steven.say("Hello")
'Hello'
>>> steven.repeat()
'Hello'
>>> steven.greet()
'Hello, my name is Steven'
>>> steven.repeat()
'Hello, my name is Steven'
>>> steven.ask("preserve abstraction barriers")
'Would you please preserve abstraction barriers'
>>> steven.repeat()
'Would you please preserve abstraction barriers'
"""
def __init__(self, name):
self.name = name
"*** YOUR CODE HERE ***"
def say(self, stuff):
"*** YOUR CODE HERE ***"
return stuff
def ask(self, stuff):
return self.say("Would you please " + stuff)
def greet(self):
return self.say("Hello, my name is " + self.name)
def repeat(self):
"*** YOUR CODE HERE ***"Use OK to test your code:
python3 ok -q PersonQuestion 2: Account
There are several things wrong with the following code! Debug the Account class to satisfy the docstring.
class Account(object):
"""A bank account that allows deposits and withdrawals.
>>> sophia_account = Account('Sophia')
>>> sophia_account.deposit(1000000) # depositing my paycheck for the week
1000000
>>> sophia_account.transactions
[('deposit', 1000000)]
>>> sophia_account.withdraw(100) # buying dinner
999900
>>> sophia_account.transactions
[('deposit', 1000000), ('withdraw', 100)]
"""
interest = 0.02
balance = 1000
def __init__(self, account_holder):
self.balance = 0
self.holder = account_holder
self.transactions = []
def deposit(self, amount):
"""Increase the account balance by amount and return the
new balance.
"""
self.transactions.append(('deposit', amount))
Account.balance = self.balance + amount
return self.balance
def withdraw(self, amount):
"""Decrease the account balance by amount and return the
new balance.
"""
self.transactions.append(('withdraw', amount))
if amount > self.balance:
return 'Insufficient funds'
self.balance = Account.balance - amount
return Account.balanceUse OK to test your code:
python3 ok -q AccountQuestion 3: Vending Machine
Create a class called VendingMachine that represents a vending
machine for some product. A VendingMachine object returns strings
describing its interactions. See the doctest below for examples:
Here's a quick explanation of some of the functions you need to implement.
restock should update the stock and return the current stock.
deposit should add money to the balance and return the current balance, unless the stock is zero, then it should inform the user the stock is zero and return the money.
vend should either tell you how much more money needs to be deposited to buy a product, or sell you a product and return the change, or let you know the machine is out of stock.
Make sure your outputs match the doctest exactly!
Hint: .format() can help you format your strings. Here's an example:
>>> name = "Alex"
>>> 'My name is {}'.format(name)
'My name is Alex'class VendingMachine:
"""A vending machine that vends some product for some price.
>>> v = VendingMachine('candy', 10)
>>> v.vend()
'Machine is out of stock.'
>>> v.restock(2)
'Current candy stock: 2'
>>> v.vend()
'You must deposit $10 more.'
>>> v.deposit(7)
'Current balance: $7'
>>> v.vend()
'You must deposit $3 more.'
>>> v.deposit(5)
'Current balance: $12'
>>> v.vend()
'Here is your candy and $2 change.'
>>> v.deposit(10)
'Current balance: $10'
>>> v.vend()
'Here is your candy.'
>>> v.deposit(15)
'Machine is out of stock. Here is your $15.'
"""
def __init__(self, product, price):
self.product = product
self.price = price
self.stock = 0
self.balance = 0
"*** YOUR CODE HERE ***"Use OK to test your code:
python3 ok -q VendingMachineQuestion 4: Arr88
In lab you created the T88ble, now you will create arr88, which are similar to numpy arrays from Data 8.
Complete the __len__, and item functions according to the docstrings.
__len__ is a special attribute, like __init__ that allows us to call len on our Arr88s to get their length!
def __len__(self):
""" Return the length of the Arr88
>>> arr88 = Arr88([1, 2, 3])
>>> len(arr88)
3
>>> arr88 = Arr88([1, 2, 3, 4])
>>> len(arr88)
4
"""
"*** YOUR CODE HERE ***"
def item(self, i):
"""
Get the item of the Arr88 at index i
>>> arr88 = Arr88([1, 2, 3])
>>> arr88.item(1)
2
>>> arr88.item(0)
1
"""
"*** YOUR CODE HERE ***"
Use OK to test your code:
python3 ok -q Arr88.__len__Use OK to test your code:
python3 ok -q Arr88.itemComplete the __add__, __mul__, and negate functions according to the docstrings.
Keep an eye out for which functions mutate the Arr88 and which don't!
__add__ and __mul__ are also special attributes, like __init__ and __len__, that allow us to use + and * on our Arr88s to add/multiply them componentwise!
def __add__(self, arr88):
""" Add two Arr88s of the same length element by element
>>> arr88a = Arr88([1, 2, 3])
>>> arr88b = Arr88([4, 5, 6])
>>> arr88a + arr88b
Arr88([5, 7, 9])
>>> arr88a # We aren't mutating arr88a
Arr88([1, 2, 3])
>>> arr88a = Arr88(['He', 'Wor', '!'])
>>> arr88b = Arr88(['llo', 'ld', ''])
>>> arr88c = arr88a + arr88b
>>> arr88c
Arr88(['Hello', 'World', '!'])
"""
# Checks that the lengths are the same
assert len(self) == len(arr88), "Arr88's of different len"
"*** YOUR CODE HERE ***"
def __mul__(self, arr88):
""" Multiply two Arr88s of the same length componentwise
>>> arr88a = Arr88([1, 2, 3])
>>> arr88b = Arr88([4, 5, 6])
>>> arr88a * arr88b
Arr88([4, 10, 18])
>>> arr88a # We aren't mutating arr88a
Arr88([1, 2, 3])
>>> arr88a = Arr88(['Na', 'Batman', '!'])
>>> arr88b = Arr88([10, 1, 5])
>>> arr88c = arr88a * arr88b
>>> arr88c
Arr88(['NaNaNaNaNaNaNaNaNaNa', 'Batman', '!!!!!'])
"""
# Checks that the lengths are the same
assert len(self) == len(arr88), "Arr88's of different len"
"*** YOUR CODE HERE ***"
def negate(self):
"""Negate an Arr88 with mutation
>>> arr88a = Arr88([1, 2, 3])
>>> arr88b = Arr88([4.0, -5.5, 0.0])
>>> arr88a.negate()
>>> arr88a
Arr88([-1, -2, -3])
>>> arr88b.negate()
>>> arr88b
Arr88([-4.0, 5.5, -0.0])
"""
"*** YOUR CODE HERE ***"
Use OK to test your code:
python3 ok -q Arr88.__add__Use OK to test your code:
python3 ok -q Arr88.__mul__Use OK to test your code:
python3 ok -q Arr88.negateComplete the apply function that returns a new list with the function applied to every element.
def apply(self, func):
""" Apply a function to an Arr88
>>> arr88a = Arr88([1, 2, 3])
>>> arr88a.apply(lambda x : x * x)
Arr88([1, 4, 9])
>>> arr88a # We aren't mutating arr88a
Arr88([1, 2, 3])
>>> arr88b = Arr88([lambda x: x, lambda x: x + 1, lambda x: x + 2])
>>> arr88c = arr88b.apply(lambda f: f(1))
>>> arr88c
Arr88([1, 2, 3])
"""
"*** YOUR CODE HERE ***"
Use OK to test your code:
python3 ok -q Arr88.applySubmit
Make sure to submit this assignment by running:
python3 ok --submit