Lab Assignment #11 Solution

Assignment Objectives




This lab will give you some hands-on practice implementing basic data compression in Python.




Getting Started




Visit Piazza and download the “bare bones” file lab11.py onto your computer. Open lab11.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 #11)




Submit your final lab11.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.




Download Instructions




Download lab11.zip from Piazza. In the zip archive, you will find all the normal files as usual (template, driver). You will also find an extra folder called test files. It is important you keep the folder as it is, and place the folder in the same directory with lab11.py and lab11 driver.py.










Part I: String Compressor (20 points)




In this problem, you will be implementing a basic data compression algorithm.




Write a function compress line(), which takes one argument, line, a string that you will need to compress it.




The algorithm works like this: take a string and start reading from the beginning, compress identical consecutive characters in the form of count of that character directly followed by that character. In the end, the original string will be shortened (hopefully!), and the function should return that shortened result.




For example, the string ’AAABBBCCC’ will be shortened to ’3A3B3C’; the string ’AAC!!?????’ will be

shortened to 2A1C2!5?; and the string ’ @@@@B ’ will be shortened to ’3 4@1B2 ’. Notice thata space is also considered a character.




Note: You may assume that only valid strings will be given as an input for the function. Also, it is very important that you do a .strip(’\r\n’) on every string. This is because the invisible newline/return characters may cause issues when you do Part II of this assignment.




Examples:




Function Call
Return Value
compress line(’ PPPPPPPPggggggggggffff+++n M\r\n’)
2 8P10g4f3+1n5 1M
compress line(’ PwwwwwwRRRRRR\r’)
3 1P6w6R
compress line(’ hhhhhhhhhhcccccccFFFFFFFFFvvvvdddd

ttttttttt\r\n’)
3 10h7c9F4v4d8 9t
compress line(’ mmmmmmmm ???? ---------- Uwwww

<<<<TTTTTTTTT SSSSSSSS FF \n’)
3 8m7 4?1 10-2 1U4w3

4<9T4 8S4 2F7
compress line(’ ######EEEE [[[[[[[S:::::::

’)
3 6#4E7 7[1S7:7
compress line(’....xx ;;;;;;;;;999922 }}}}}}}}}cccccKKK

3\r\n’)
4.2x4 9;49227 9}5c3K8

13
compress line(’II4*********)))))))vvvvvvvLLLLLLLLLpp

]]]]]]]\n’)
2I149*7)7v9L2p3 7]
compress line(’ XXX ddssPPPPPP\r’)
1 3X7 2d2s6P
compress line(’(((((((((( HHHHH ????????....

FFUUUUUUUUUU LLLLLL\n’)
10(2 5H2 8?4.3 2F10U7

6L
compress line(’ 8888 yyyyyyyyyy,,,,,,,,

l2222222\n’)
2 485 10y8,7 1l72
compress line(’ gggggggmmmmmm&&&&&&33333

yyyyyyyyiiiiiii\r\n’)
1 7g6m6&531 8y7i
compress line(’QQQ000 [[[;;::::CCRRRRRRR%%% \r\n’)
3Q302 3[2;4:2C7R3%3
compress line(’ ggggggggggwwwwwwwwJJJJ\r\n’)
2 10g8w4J
compress line(’zzzzzFFFFU (( ))))))XXXXXX

pssssssssss VVVVVVVVV\r’)
5z4F1U2 2(5 6)6X6

1p10s8 9V
compress line(’ H w RRRRRRRR\n’)
1 1H6 1w3 8R
compress line(’ PPPPPPPPPPjjjjjj IIIIllllllll\r\n’)
1 10P6j1 4I8l
compress line(’ +++++$$$$ zzzzzzzl8888888888\r\n’)
2 5+4$3 7z1l108
compress line(’ WWWWWWW dddddd !!! ......VVVVVV

wwwwww\n’)
3 7W6 6d1 3!3 6.6V6

6w7
compress line(’ zz\{oo\n’)
1 2z1\{2o









Part II: File Compressor (20 points)




Write a function compress file(), that takes one argument, filename, which is the name of the file you need to compress.




In this part, you should read the file line by line, compress each line as described in Part I, and append each compressed line into a list. In the end, you should return the result list that consists of all the compressed lines, in the correct order. You should call the function you wrote in Part I to compress each individual line for you.

Examples: Due to very long outputs, please consult the lab driver for examples.




Note: If you use MacOS, you may find the format getting messed up when you open one of the test files. Try to open the .txt files in Pycharm itself or some kind of text editor like Atom, and it should look correct.







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.