Lecture 15 — Exercises

Solutions to the problems below must be sent to Submitty for automatic scoring. A separate file must submitted for each problem. Solutions must be submitted by 4 pm on Tuesday, March 20.

1. What is the output of the following Python code? Write the answer by hand before you type it into the Python interpreter. One thing that will be hard to guess is the order of the sets, especially when the set mixes integers and strings. Therefore, you pretty much have to run the code to make sure you have the order right. (At the moment, our use of Submitty is not sophisticated enough to allow random order.) This means you get the points almost for free, but you should make the effort to be sure you understand what is happening.

   s1 = set([0,1,2])
   s2 = set(range(1,9,2))
   print('A:', s1.union(s2))
   
   print('B:', s1)
   
   s1.add('1')
   s1.add(0)
   s1.add('3')
   s3 = s1 | s2
   print('C:', s3)
   
   print('D:', s3 - s1)
   

   Note that this example does NOT cover all of the possible set operations. You should generate and test your own examples to ensure that you understand all of the basic set operations.

2. Write a Python program that asks the user for two strings: (1) the name of a file formatted in the same way as the IMDB data, and (2) a string that is the start of a last name. The program should output the number of different last names that are in the file and it should output the number of different names that start with the string. Your program must use a set and you may / are encouraged to start from the code written during lecture.

   We define a last name to be everything up to the first comma in the name. (Some names will not have commas in them, and be careful to avoid adding empty last names to the set.) For example,

   Downey Jr., Robert | Back to School |      1986
   Downey Sr., Robert   | Moment to Moment  | 1975
   Downey, Elsie    | Moment to Moment     |  1975
   

   would result in three different last names, Downey Jr., Downey Sr. and Downey.

   Here is one example of running our solution:

   Data file name: imdb/imdb_data.txt
   Prefix: Down
   48754 last names
   10 start with Down
   

   Before uploading your Python file to Submitty you should test using the data files (or restricted versions of them!) we provided for Lecture 15 on the Piazza page. On Submitty we will test with different files and examples.