Lab Assignment #10 solution

Assignment Objectives




This lab assignment will give you some practice working with classes and objects.




Getting Started




Visit Piazza and download the “bare bones” file lab10.py onto your computer. Open lab10.py in PyCharm and fill in the following information at the top:




1. your first and last name as they appear in Blackboard




2. your Net ID (e.g., jsmith)




3. your Stony Brook ID # (e.g., 111999999)




4. the course number (CSE 101)




5. the assignment name and number (Lab #10)




Submit your final lab10.py file to Blackboard by the due date and time. Late work will not be graded. Code that crashes and cannot be graded will earn no credit.




Preliminaries




Throughout this lab you will be working with the class given below, which defines the characteristics of a package being shipped in the mail:




class Package:

def init (self, sender, recipient, cost=0, distance=0):

self.sender = sender self.recipient = recipient self.cost = cost self.distance = distance




sender and recipient are strings that specify the cities where the sender and recipient of the package live, respectively. cost is the cost to ship the package, and distance is the distance that the package traveled.




This class definition is available in the file package.py. DO NOT CHANGE THE CONTENTS OF THAT FILE.

Part I: Shipping Packages (20 points)




Complete the function shipping cost(), which takes two arguments, in this order:




1. packages: a list of Package objects for which we need to compute the costs to ship.




2. cost schedule: a list of 4 integers that represent how much it costs to ship a package various distances:




Value
Meaning
cost schedule[0]
the cost to ship a package < 100 miles
cost schedule[1]
the cost to ship a package ≥ 100 miles, but < 300 miles
cost schedule[2]
the cost to ship a package ≥ 300 miles, but < 500 miles
cost schedule[3]
the cost to ship a package ≥ 500 miles



The function has two purposes:




1. It computes and returns the total cost to ship all of the packages given in the packages list and returns that total.




2. It computes the cost to ship each package in the packages list and updates the cost attribute of each Package accordingly. For example, suppose we compute that it will cost $15 to ship packages[i]. The function will set packages[i].cost = 15




You may assume that packages always contains at least one Package object.




Example:




Function call:




shipping_cost([Package("Monmouth", "Appleby", cost=0, distance=144), Package("Larkinge", "Ballachulish", cost=0, distance=65), Package("Malrton", "Auchtermuchty", cost=0, distance=872), Package("Monmouth", "Anghor Thom", cost=0, distance=937)], [10, 16, 37, 49])}




Return value: 124




Updated packages list:




[Package("Monmouth", "Appleby", cost=16, distance=144), Package("Larkinge", "Ballachulish", cost=10, distance=65), Package("Malrton", "Auchtermuchty", cost=49, distance=872), Package("Monmouth", "Anghor Thom", cost=49, distance=937)]










Part II: Tracking Packages (20 points)




Complete the function package tracking(), which takes three arguments, in this order:




1. packages info: a list of tuples containing two values: the name of the city that a package was sent from and the name of the city that the package was sent to.

2. locations: a dictionary that maps a city’s name to its 2D coordinate position, stored as a tuple.




3. cost schedule: a list of 4 integers that represent how much it costs to ship a package various distances:




Value
Meaning
cost schedule[0]
the cost to ship a package < 100 miles
cost schedule[1]
the cost to ship a package ≥ 100 miles, but < 300 miles
cost schedule[2]
the cost to ship a package ≥ 300 miles, but < 500 miles
cost schedule[3]
the cost to ship a package ≥ 500 miles



The function iterates over the packages list and incrementally builds a list of Package objects that represent packages being sent with the given senders and recipients. For each new Package object that the function creates, the function consults the location dictionary to help it compute the distance that each package will travel. The function can then set the distance field of each Package object accordingly. Next, using the cost schedule list, the function sets the cost field of each Package object. Finally, the function returns the list of Package objects it created.




We will use the 2D Euclidean distance as the distance between two cities. (This isn’t accurate because the Earth is round, but it’s OK!) Given the coordinate positions (x1, y1 ) and (x2, y2 ) of two points, the distance between the

points is given as p(x1 − x2 )2 + (y1 − y2)2.

Example: Function call: package_tracking(

[(’Appleby’, ’Satbury’),

(’Northpass’, ’Berkton’), (’Eanverness’, ’Satbury’)],




{’Appleby’: (58, 189), ’Berkton’: (84, 13),

’Ballachulish’: (12, 149), ’Aerilon’: (28, 77),

’Garennton’: (173, 68), ’Malrton’: (124, 133),

’Peltragow’: (194, 181), ’Paentmarwy’: (191, 151),

’Eanverness’: (134, 50), ’Satbury’: (25, 181),

’Bracklewhyte’: (47, 124), ’Larkinge’: (8, 157),

’Burnsley’: (71, 5), ’Erith’: (2, 181),

’Monmouth’: (160, 13), ’Northpass’: (84, 45),

’Jedborourgh’: (87, 163), ’Anghor Thom’: (109, 10),

’Auchtermuchty’: (140, 189), ’Murrayfield’: (164, 83)},




[18, 21, 24, 48]

)




Returned list:




[Package("Appleby", "Satbury", cost=18, distance=33.95585369269929), Package("Northpass", "Berkton", cost=18, distance=32.0), Package("Eanverness", "Satbury", cost=21, distance=170.41713528867922)]

Notes:




Consider the Package class again for a moment:




class Package:

def init (self, sender, recipient, cost=0, distance=0):

self.sender = sender self.recipient = recipient self.cost = cost self.distance = distance




We note that the constructor ( init ()) has two default arguments for the cost and distance attributes. In practice this means that we can construct a Package object with only two attributes and set the cost and distance attributes later:




new_package = Package(’New York’, ’Los Angeles’)

# ... other code here, possibly ... and then:

new_package.cost = 50 new_package.distance = 3000




or we can construct the object with all 4 attributes at once, if we like:




new_package = Package(’New York’, ’Los Angeles’, 50, 3000)




You can use either approach; both are acceptable.







How to Submit Your Work for Grading




To submit your .py file for grading:




1. Login to Blackboard and locate the course account for CSE 101.




2. Click on “Assignments” in the left-hand menu and find the link for this assignment.




3. Click on the link for this assignment.




4. Click the “Browse My Computer” button and locate the .py file you wish to submit. Submit only that one

.py file.




5. Click the “Submit” button to submit your work for grading.







Oops, I messed up and I need to resubmit a file!




No worries! Just follow the above directions again. We will grade only your last submission.