Lecture 16 - Exercises

16A - split and join

1. What does the following print?

   print("_".join("88r4if4r462".split("r4")))

16B - Reading and Writing Files

2. Suppose the file rick.txt contains:

   Never gonna give you up

   What is the output of the following code?

   print(open("rick.txt", "r").read(5).split("e"))

3. Assume a file called fin.txt exists in the same directory as the program below, and has the following contents:

   Start: 4pm
   End: 7pm
   3h

   What does the following program print?

   fin = open("fin.txt", 'r')
   fot = open("fot.txt", 'w')
   
   for line in fin:
       fl = line.strip().split(': ')
   
       fot.write(fl[-1])
       fot.write(fl[0])
   
   fot.close()
   fin.close()
   
   fot = open("fot.txt", 'r')
   a = fot.read(3)
   fot.seek(8)
   print(a, fot.read())
   fot.close()

Problems

1. Implement the following function:

   def split_address(addr_line):
       """ Split the postal address in address_line into its
       component pieces. Return a tuple of strings containing:
           (number, street, city, state, zip).
       Precondition: the address matches the following format:
           "<number> <street>, <city> <state> <zip>"
       Example: split_address("516 High St, Bellingham WA 98225")
       => ("516", "High St", "Bellingham", "WA", "98225") """

2. Download test.txt. Write a program that counts and prints the number of unique lines in the file. Be sure that the text file and your Python program are saved in the same directory.

3. Implement the following function:

   def grep(string, filename):
       """ Print all lines of the file filename that contain the given string.
       Precondition: the file exists. """

4. Download AboutYou.csv. Write a Python program to calculate the average number of quarters at Western among each of three groups of students:

   • students who are planning to major in CS
   • students who are considering a CS major
   • students who are not planning to major in CS

5. Implement the following function:

   def spellcheck(in_filename, out_filename wordlist):
       """ Write a spellchecked version of in_filename to
       out_filename. For each word in the input file, write
       it as-is to the output file if it is in the wordlist;
       otherwise, write it to the output file in ALLCAPS to
       indicate that it's not in the wordlist. """