Lab 8: Reading & Writing Files

The lecture notes on files may be helpful during this part of the lab.

To get some practice reading from and writing to files, we've supplied you with the following text files in the starter directory:

• nums.txt Contains the numbers one through 10, each on its own line.
• nums2.txt An alternate version of nums.txt.
• birds.txt Contains a list of bird names, one per line.
• fruit.txt Contains a list of fruits and their categories, one per line, with the fruit and category names separated by a single space.
• metals.txt Contains a list of a few metallic elements, along with their densities, with a colon and a space in between the element name and density value.
• meetings.txt Contains a list of meetings, with a meeting name, a start time, and a duration separated by commas. The time of day is two integers (one for the hour and one for the minutes) separated by a colon, while the duration is a floating-point number representing hours.

You will have to create your own code file for this part of the lab, called files.py.

Work through the exercises below...

showTop

Write a function named showTop which accepts a file name as an argument, and which reads that file and prints out the first three lines of text in the file. Test it on nums.txt, and you should see:

one
two
three

showBottom

showBottom should work like showTop, except it should print the last three lines from the file instead of the first three. Testing on nums.txt should result in:

eight
nine
10

listLines

listLines should accept a file name as an argument, and print the entire contents of that file, but it should add a line number at the start of each line, separated from the actual line by a single space. The first line number should be 1 (not 0). Here's what the result would look like if applied to nums.txt:

1 one
2 two
3 three
4 4
5 five
6 six
7 seven
8 eight
9 nine
10 10

copyFile

copyFile should take two different file names as arguments: the first argument is the name of the original file, and the second argument is the name of the file that will store a copy of the original file. You should open the first file, read in the contents, then open the second file, and write out a copy of the first file (so that at the end, the two files end up as copies of each other). Be careful that you don't accidentally overwrite one of the starter files when you're testing this! It won't have any return value or printed output... but you should check that it creates an exact copy of the file you're trying to copy (you could open both files in a text editor). You could test it with:

copyFile("birds.txt", "moreBirds.txt")

Table of Contents

• Lab 8 Home
• Part 0: Warm-Up
• Part 1: Tests & List Comprehensions
• Part 2: File Exercises
• Part 3: Secret Message
• Extra: Additional Exercises
• Knowledge Check