Programming and Computation II Lab #2

CMPSC-132: Programming and Computation II

Lab #2

Read the instructions carefully before starting the assignment. Make sure your code follows the
stated guidelines to ensure full credit for your work.
Instructions:
- The work in this lab must be completed alone and must be your own.
- Watch the video lectures before you start this assignment
- Download the starter code file from the LAB2 Assignment on Canvas. Do not change the
function names or given started code on your script.
- A doctest is provided as an example of code functionality. Getting the same result as the
doctest does not guarantee full credit. You are responsible for debugging and testing your
code with enough data, you can share ideas and testing code during your recitation class.
As a reminder, Gradescope should not be used to debug and test code!
- Each function must return the output (Do not use print in your final submission, otherwise
your submissions will receive a -1 point deduction)
- Do not include test code outside any function in the upload. Printing unwanted or illformatted data to output will cause the test cases to fail. Remove all your testing code
before uploading your file (You can also remove the doctest). Do not include the
input() function in your submission.
Goal:
[5 pts] Write the class VendingMachine that will represent a typical vending machine (item
number, price, stock). An instance of VendingMachine has access to five methods, newStock,
getStock, purchase, deposit and restock that will describe its interaction with the user returning
strings. This vending machine does not give you money back if you don’t make a purchase. Tip:
use the string format method to construct the strings
Vending Machine notes:
• When creating an instance of this class, the machine is empty, thus, calling getStock, purchase
and deposit simply return out of stock messages:

 >>> x=VendingMachine()
 >>> x.purchase(215)
 'Machine out of stock'
 >>> x.deposit(10)
 'Machine out of stock. Take your $10 back'
 >>> x.getStock()
 'Machine out of stock'
 >>> x.restock(215, 9)
 'Invalid item'
• newStock is used only when the registering a new item. If an item is out of stock or still has
stock, using newStock will return a message to the user. For already registered items, you use
the restock method. Restock returns an error when the item is not in the dictionary
 >>> x.newStock(215,2.50,2)
 'Current 215 stock: 2'
 >>> x.restock(215, 1)
 'Current item stock: 3'
 >>> x.restock(5, 1)
 'Invalid item'
 >>> x.getStock()
 {215: [2.5, 3]}

 # User deposits 7.5 and purchases 3 items of 215

 >>> x.getStock()
 {215: [2.5, 0]}
 >>> x.newStock(215,2.50,2)
 'Item already registered'
 >>> x.newStock(156,3,3)
 'Current 156 stock: 3'
 >>> x.getStock()
 {215: [2.5, 0], 156: [3, 3]}
• If all products are out of stock, deposit returns an out of stock message
 >>> x.getStock()
 {215: [2.5, 0], 156: [3, 0]}
 >>> x.deposit(10)
 'Machine out of stock. Take your $10 back'
• purchase uses quantity=1 as a default value, which can be overwritten by providing the second
argument. Before completing a purchase, machine has to check if the item is valid, if it is on
stock and if the user has enough balance.
 >>> x.getStock()
 {215: [3, 1], 156: [3.5, 4]}
 >>> x.purchase(56)
 'Invalid item'
 >>> x.purchase(215)
 'Please deposit $3'
 >>> x.deposit(1)
 >>> x.purchase(215)
 'Please deposit $2'
 >>> x.deposit(10)
 >>> x.purchase(215)
 'Item dispensed, take your $5'
 >>> x.purchase(215)
 'Item out of stock'
 >>> x.getStock()
 {215: [3, 0], 156: [3.5, 4]}
• getStock returns a dictionary where the key is the item and the value is the list [price, stock]
• purchase will ask for the needed money to complete a purchase if enough items are in stock,
otherwise, it returns the current stock of the item (for example 3 items in stock and attempting
to purchase 4)
• Once the user completes one purchase, machine returns remaining balance
• For more examples of functionality, check the doctest in the starter code
• Quotes mean method returned a string, no need to append them in your code
• Return output with the sentences provided. Solution is not case sensitive, which means
Balance: $10 is the same as balance: $10, but is not the same as Balance= $10
[5 pts] Write the class Complex that supports the basic complex number operations. Such
operations are addition (+), subtraction (-), multiplication (*) and division (/) of complex numbers,
and addition (+), subtraction (-) and multiplication (*) of a complex by a scalar (float or int). All
methods must return (not print) the result. Class also supports the rich comparison for equality
(= =)
- Check the doctest for object behavior examples.
- You must use the special methods for those 5 operators in order to override their behavior.
- You will need other special methods to achieve a legible object representation (what you
see when printing and returning the object).
- Addition, subtraction and multiplication by scalar and by another complex number use the
same operator, so you must check the type of the object in order to decide which operation
you have to perform
- Rich comparison returns a Boolean value
- The rest of the methods must return a new Complex object, this means the original
objects should not change after the operation is performed.
- Test your code, this is how you ensure you get the most credit out of your work!!
- When performing an invalid operation, return None
- You are not allowed to modify the constructor or any given code.
- Note that to support number (+, - or *) Complex, you are going to need 3 other special
methods that can reuse code from the Complex (+, - or *) number operations. Hint: Section
3.3.1. Basic customization (__eq__) and Full Section 3.3.8. Emulating numeric types in
https://docs.python.org/3/reference/datamodel.html#emulating-numeric-types
In addition, write the property method conjugate into the Complex class. The complex conjugate
of the complex number z = x + yi is given by x – yi
Remember, you are not allowed to modify the given constructor. The method conjugate must
be a property method, otherwise, no credit will be given. Property methods are discussed in the
video lectures!
You can visit https://www.varsitytutors.com/hotmath/hotmath_help/topics/operations-withcomplex-numbers for complex number formulas
General note: Start by watching the lectures. Do not overthink this assignment, you don’t have to
come up with a complex algorithm to solve it. Just follow the formulas and directions, the purpose
of this assignment is to familiarize you with object-oriented programming syntax
Deliverables:
• Submit your code with the file name LAB2.py to the Lab2 Gradescope assignment before
the due date