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CptS355 – Lab 3 (Python)
Weight: Lab3 will count for 1.5% of your course grade.
This assignment provides experience in Python programming.
Turning in your lab submission
This lab involves 6 programming problems and your solution will consist of a sequence of function
definitions for the given problems. You should implement as many of the problems as you can. As
explained in the “Grading” section, 4 correct solutions are sufficient to earn full points in the lab. Note
that some problems have sub-parts; you should complete all parts to get credit for those problems.
You will write all your functions in the attached Lab3.py file. Attached file,
Lab3SampleTests.zip, includes Python unittest tests for each problem. Make sure to test
your code before you submit. Please refer to the “Testing your functions” section at the end of this
document.
To submit your assignment, please upload the file Lab3.py on the Lab3 (Python) dropbox on Canvas
(under Assignments). You may turn in your lab submission up to 3 times. Only the last one submitted
will be graded.
Grading
The lab assignments will be auto-graded using automated tests. Your lab grade will be calculated as
follows:
– When you submit the lab, you will automatically earn 60 points.
– For every correct solution that passes all test cases, you will earn 10 points. If your function fails
even a single test case, you will not be able to earn points for that question.
– The lab includes 6 programming problems. You can implement as many of the lab problems as you
want. However, 4 correct answers are sufficient to earn full points (100) in the lab. No extra credit
will be given for additional solutions.
– However, submitting solutions for more than 4 problems will improve your chance to obtain 100%
score (in case one of the test cases fail for the other problems).
– The Lab Zoom sessions are optional. You can work on the lab problems yourself or with your friends
and submit your solutions on Canvas.
Problems:
1. getNumCases(data,counties,months)
Assume that you work for a “Healthcare Data Analytics” company and you write scripts to process
various dataset. In your analysis, you use the CDC’s COVID-19 dataset. For example, the following
dataset reports the monthly new COVID cases in year 2020 for some counties in WA.
CDCdata =
{‘King’:{‘Mar’:2706,’Apr’:3620,’May’:1860,’Jun’:2157,’July’:5014,’Aug’:4327,’Sep’:2843},
‘Pierce’:{‘Mar’:460,’Apr’:965,’May’:522,’Jun’:647,’July’:2470,’Aug’:1776,’Sep’:1266},
‘Snohomish’:{‘Mar’:1301,’Apr’:1145,’May’:532,’Jun’:568,’July’:1540,’Aug’:1134,’Sep’:811},
‘Spokane’:{‘Mar’:147,’Apr’:222,’May’:233,’Jun’:794,’July’:2412,’Aug’:1530,’Sep’:1751},
‘Whitman’ : {‘Apr’:7,’May’:5,’Jun’:19,’July’:51,’Aug’:514,’Sep’:732, ‘Oct’:278} }
The keys of the dictionary are the county names, and the values are the dictionaries which include
the monthly new COVID cases. Note that some counties may not have any new cases in some
months.
Define a function, getNumCases, which calculates the total number of new cases for a given list
of counties during a given list of months. For example:
getNumCases(CDCdata,[‘Whitman’],[‘Apr’,’May’,’Jun’]) returns 31, and
getNumCases(CDCdata,[‘King’,’Pierce’],[‘July’,’Aug’]) returns 13587.
(Important note: Your function should not hardcode the county names and the month
abbreviations. It should simply iterate over the keys that appear in the given dictionary. You will be
deducted points if you hardcode any keys. )
You can start with the following code:
def getNumCases(data,counties,months):
#write your code here
2. getMonthlyCases(data)
Assume, your supervisor asks you to reformat the data and create a dictionary that includes the
number of cases for each county, organized by months. For example, when you reformat the above
dictionary you will get the following.
{‘Mar’:{‘King’:2706,’Pierce’:460,’Snohomish’:1301,’Spokane’:147},
‘Apr’:{‘King’:3620,’Pierce’:965,’Snohomish’:1145,’Spokane’:222,’Whitman’:7},
‘May’:{‘King’:1860,’Pierce’:522,’Snohomish’:532,’Spokane’:233,’Whitman’:5},
‘Jun’:{‘King’:2157,’Pierce’:647,’Snohomish’:568,’Spokane’:794,’Whitman’:19},
‘July’:{‘King’:5014,’Pierce’:2470,’Snohomish’:1540,’Spokane’:2412,’Whitman’:51},
‘Aug’:{‘King’:4327,’Pierce’:1776,’Snohomish’:1134,’Spokane’:1530,’Whitman’:514},
‘Sep’:{‘King’:2843,’Pierce’:1266,’Snohomish’:811,’Spokane’:1751,’Whitman’:732},
‘Oct’:{‘Whitman’:278}}
Define a function getMonthlyCases that reformats the CDC data as described above. Your
function should not hardcode the county names and the month abbreviations.
(The items in the output dictionary can have arbitrary order.)
3. mostCases(data)
Assume, you would like to find the month that had the maximum total number of new cases in all
counties. For example:
mostCases(CDCdata) returns (‘July’, 11487)
#i.e., July has the max number of total new cases, which is 11487.
Your function definition should not use loops or recursion but use the Python map and reduce
functions. You should also use the getMonthlyCases function you defined in part(b). You may
define and call helper (or anonymous) functions, however your helper functions should not use
loops or recursion.
4. Dictionaries and Lists
a) searchDicts(L,k)– 5%
Write a function searchDicts that takes a list of dictionaries L and a key k as input and checks
each dictionary in L starting from the end of the list. If k appears in a dictionary, searchDicts
returns the value for key k. If k appears in more than one dictionary, it will return the one that it
finds first (closer to the end of the list).
For example:
L1 = [{“x”:1,”y”:True,”z”:”found”},{“x”:2},{“y”:False}]
searchDicts(L1,”x”) returns 2
searchDicts(L1,”y”) returns False
searchDicts(L1,”z”) returns “found”
searchDicts(L1,”t”) returns None
You can start with the following code:
def searchDicts(L,k):
#write your code here
b) searchDicts2(tL,k) – 10%
Write a function searchDicts2 that takes a list of tuples (tL) and a key k as input. Each tuple in
the input list includes an integer index value and a dictionary. The index in each tuple represent a
link to another tuple in the list (e.g. index 3 refers to the 4th tuple, i.e., the tuple at index 3 in the list)
searchDicts2 checks the dictionary in each tuple in tL starting from the end of the list and
following the indexes specified in the tuples.
For example, assume the following:
[(0,d0),(0,d1),(0,d2),(1,d3),(2,d4),(3,d5),(5,d6)]
0 1 2 3 4 5 6
The searchDicts2 function will check the dictionaries d6,d5,d3,d1,d0 in order (it will skip
over d4 and d2) The tuple in the beginning of the list will always have index 0.
It will return the first value found for key k. If k is couldn’t be found in any dictionary, then it will
return None.
For example:
L2 = [(0,{“x”:0,”y”:True,”z”:”zero”}),
(0,{“x”:1}),
(1,{“y”:False}),
(1,{“x”:3, “z”:”three”}),
(2,{})]
searchDicts2 (L2,”x”) returns 1
searchDicts2 (L2,”y”) returns False
searchDicts2 (L2,”z”) returns “zero”
searchDicts2 (L2,”t”) returns None
(Note: I suggest you to provide a recursive solution to this problem.
Hint: Define a helper function with an additional parameter that hold the list index which will be
searched in the next recursive call.)
You can start with the following code:
def searchDicts2(L,k):
#write your code here
5. getLongest(L) – 10%
Write a function, getLongest, which takes an arbitrarily nested list of strings (L) and it returns the
longest string in L. Note that the longest string can be found at any nesting level, so your function should
recursively check all sublists. You should not assume a max depth for the nesting. If there are more than
one string that have the max length, you should return the one that appears earlier in the list.
For example:
getLongest([‘1′,[’22’,[‘333’,[‘4444′,’55555’,[‘666666′]],’7777777′],’4444′],’22’])
returns ‘7777777’
getLongest([[‘cat’,[‘dog’,’horse’],[‘bird’,[‘bunny’,’fish’]]]])
returns ‘horse’
You can start with the following code:
def getLongest (L):
#write your code here
6. Iterators
apply2nextN()– 20%
Create an iterator that represents the aggregated sequence of values from an input iterator. The iterator
will be initialized with a combining function (op), an integer value (n) , and an input iterator (input).
When the iterator’s __next__() method is called, it will combine the next “n” values in the “input“
by applying the “op” function and it will return the combined value. The iterator should stop when it
reaches the end of the input sequence. If the input sequence is infinite, the apply2nextN will return an
infinite sequence as well.
For example:
iSequence = apply2nextN(lambda a,b:a+b, 3, iter(range(1,32)))
# iSequence represents the sequence [6, 15, 24, 33, 42, 51, 60, 69, 78, 87, 31]
iSequence.__next__() # returns 6
iSequence.__next__() # returns 15
iSequence.__next__() # returns 24
rest = []
for item in iSequence:
rest.append(item)
# rest is [33, 42, 51, 60, 69, 78, 87, 31]
strIter =iter(‘aaaabbbbccccddddeeeeffffgggghhhhjjjjkkkkllllmmmm’)
iSequence = apply2nextN(lambda a,b:a+b, 4, strIter)
iSequence.__next__() # returns ‘aaaa’
iSequence.__next__() # returns ‘bbbb’
iSequence.__next__() # returns ‘cccc’
rest = []
for item in iSequence:
rest.append(item)
# rest is [‘dddd’,’eeee’,’ffff’,’gggg’,’hhhh’,’jjjj’,’kkkk’,’llll’,’mmmm’]
You can start with the following code:
class apply2nextN ():
#write your code here
Testing your functions
We will be using the unittest Python testing framework in this assignment. See
https://docs.python.org/3/library/unittest.html for additional documentation.
The file Lab3SampleTests.py provides some sample test cases comparing the actual output with
the expected (correct) output for some problems. This file imports the Lab3 module (Lab3.py file)
which will include your implementations of the given problems.
In Python unittest framework, each test function has a “test_” prefix. To run all tests for problem
1, execute the following on the command line.
python -m unittest Q1_tests.py
You can run tests with more detail (higher verbosity) by passing in the -v flag:
python -m unittest -v Q1_tests.py
Repeat the above for other lab problems by changing the test file name, i.e. , Q2_tests.py,
Q3_tests.py, etc.
In this assignment, we simply write some unit tests to verify and validate the functions. If you would like
to execute the code, you need to write the code for the “main” program. Unlike in C or Java, this is not
done by writing a function with a special name. Instead the following idiom is used. This code is to be
written at the left margin of your input file (or at the same level as the def lines if you’ve indented
those.
if __name__ == ‘__main__’:
…code to do whatever you want done…

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