Lab 1: Linux, HTML, Python Programming, and Numeric Operations

Objective: Preparing for Lab

Review Lab 0 if you don't remember how to use the lab machines.

After logging into the lab machine in person and opening a terminal OR remotely logging into one of the lab machines, run labhelp.

Objective: Set up for Programming

1. Open a terminal (if you haven't already).
2. Create a directory called lab1 in your cs111 directory. Your programs and the output for this lab will all be saved in the lab1 directory.
3. Copy all the files from the /csci/courses/cs111/handouts/lab1/ directory that end in .py into your lab1 directory.
   (Note: I made a shortcut for cs111 so you don't need to type the long course name.)

Objective: Introduction to the Python Interpreter (15 points)

On our system, you have two main options for writing Python programs:

1. write your programs in a text editor (e.g., emacs) and use the terminal to run Python. This is what I will tend to do in class.

   OR

2. write your programs in IDLE, using its shell to run the programs and then restart the shell to demonstrate your program working.

For your lab work, use IDLE.

Using the Interpreter in Interactive Mode

In a terminal, navigate to your directory for this lab, which you set up earlier. (The directory should be ~/cs111/lab1.)

To open Python's integrated development environment IDLE, use the command idle &

Recall: what does the & allow you to do?

You can use the interpreter in interactive mode to try out expressions before using them in a script. IDLE labels the interactive mode as "Python Shell". In IDLE, the main window--opened by default on start--is the interactive Python interpreter.

Type the following expressions at the Python interpreter prompt, one line at a time, and note what the interpreter returns:

• 26
• 1.414
• 3/4
• 3//4
• 'Hello there!'
• 'Hello ' + 'there!'
• 'Hi' * 4
• 'Hi' + 4
• 3/0
• 3 */ 4
• .1+.1+.1
• print("Hello, world!")

Save the output from the interpreter in a file called interactive_practice.out.
Make sure that this file is saved in the appropriate directory (~/cs111/lab1).
You won't see the file if you try to open the file -- make sure you select all files in the drop down box.

Using the Interpreter in Batch Mode

• Now, still in IDLE, open the file practice.py and execute the program.

  Note that the output from executing practice.py is after all the output from your earlier practice.

• Close IDLE's interactive Python window and re-execute practice.py. This has the net effect of clearing the window so as not to pollute the output you'll print out when you submit the lab.

Save the output from the interpreter in a file called practice.out. Again, make sure that this file is saved in the appropriate directory (~/cs111/lab1).

Objective: Writing Your Own First Programs

• (10 points) Copy practice.py into a file called practice2.py. Modify the program in the following ways:
  1. Change the first print statements to display another expression and value in the first statement and that same expression that results in that value in the second statement.
  2. Change the next two print statements to print out another emotion or adjective besides "happy".
  3. Modify the comments at the top of the program appropriately.

  After you are sure that your program works and you have saved your program, start a new IDLE shell by closing the [current] shell and executing your program. Demonstrate that your program works. Save the output from the shell in a file called practice2.out.

• (10 points) Write a Python program called info.py that prints out information about yourself. The info printed should list your name, favorite pop culture icon, favorite color, and favorite dwarf (Sleepy, Sneezy, Happy, Grumpy, Dopey, Bashful, or Doc). Don't forget to document your program appropriately!

  Best practice: Use four separate print statements on four separate lines to print this information.

  The output should look something like:

  Name: Sara Sprenkle
  Favorite pop culture icon: Tina Belcher
  Favorite color: purple
  Favorite dwarf: Doc
  

  After you are sure that your program works and you have saved your program, close the IDLE shell and re-execute the program. Save the output from the shell in a file called info.out.

Objective: Arithmetic Operations in Python

1. (15 pts) This problem has several parts. You will create a program (i.e., a script) in the first step and modify it for each subsequent step. Note how the progression of steps for this problem adheres to the good development practices we dicussed in class. Submit one program and one output file. I'll know you did the steps from your comments.
   1. Create three variables (i, j, and result) to calculate and display result = i² + 3j - 5 for the case where i=7 and j=2. Your code will not look exactly like this formula. Display the result and verify that the result is what you expect. Consider if you were the user of the program and make the program display appropriate output. Put the answer/output in a comment.
   2. Change the name of the variable i to i21. Be sure to change the name everywhere the variable is used. Execute it to verify it still works.
   3. Now edit the Python script again and change the variable name to 21i. What error message do you get? Record in comments the error message and why the error message occurred.
   4. Revert your program back to a correct variable name.
   5. Make sure that a user looking at your program's execution/output would understand what the program did.
2. (10 pts) How do you measure, measure a year? The musical Rent asks how you would measure a year and suggests love as the metric. Since we don't have a primitive data type that represents love, we'll measure a year in minutes. Write a program that computes (or calculates) the number of minutes in a year and plugs it into part of the chorus of Seasons Of Love.

   Note: do not recompute the number of minutes each time it is used in the chorus. Compute the minutes once and save it in a variable that you use in the print statements.

   Output should look like (which is not exactly the same as the actual song's lyrics):

   525600 minutes, 525600 moments so dear.
   525600 minutes - how do you measure, measure a year? 
   

3. (15 pts) MLB Hall of Famers. Rickey Henderson was voted into the Major League Baseball Hall of Fame in 2009. At one time Henderson was the career leader in three major offensive categories: runs, stolen bases, and walks. (Barry Bonds passed him in walks.)

   Henderson stole 1406 bases and was caught 335 times. Lou Brock is second with 938 stolen bases and 307 caught stealing.

   Calculate and display Henderson's and Brock's successful base stealing percentages. Then, display the difference in their percentages.

   Think about how to model the problem. What are you given? What do you need to represent? Create variables for what you need to model (and think about their data types). What do you need to output?

   Note: The calculated numbers are not very pretty when displayed. We'll learn how to format the output more nicely later this term.

Finishing up: What to turn in for this lab

You should be in the terminal (not the Python shell) to execute the following commands. You should be in your cs111/ directory.

1. If you're not already, go into your cs111 directory. Create the printable file of your lab using the command:
   createPrintableLab <labname>
   In this case, the lab name is lab1.

   Putting it all together, the command you should execute is
   createPrintableLab lab1

   The script createPrintableLab creates a condensed version of your lab in a postscript file called lab1.ps and then converts the file to pdf in lab1.pdf. To save paper, the script puts two pages on a piece of paper. The script also highlights the Python code appropriately.

   View the compiled printout using the command evince lab1.ps &
   evince allows you to view postscript files, which are suitable for printing. You should verify that the file "looks correct", i.e., no "garbage characters" and that your file is not be more than a few pages. Otherwise, you're printing too much. See the instructor or student assistant if you're having trouble.

   Review your printout with Professor Sprenkle before moving on. OR, complete the next step and let her know that you have submitted your file so she can check it out.
   If you make changes to your files, you should run the scripts to create a printable lab and the turnin script.

   Cleanup: jEdit and IDLE may make backup files. The backup files have an "~" appended to the name of your file. When printing, if you see any files that end in ~, tell us and we will help you delete the files. Don't worry if you don't have these files.

2. Submit your lab1 directory to your turnin directory so that I can see your files by running the command turnin lab1
   If everything is set up correctly, you copied your lab1 directory PLUS the printable lab into your turnin directory. If you run the script again, it will create a backup of the previous submission and copy your current directory.
3. Print out your lab submission. Open up evince again using evince lab1.ps Select the print icon and choose to print to HPLaserJetIntroLab
4. Write out and sign the honor pledge on the print out. Staple all pages together.

Labs are due at the beginning of Friday's class. The electronic version should be in the turnin directory before 9:40 a.m. on Friday.

Ask well before the deadline if you need help turning in your assignment!

Grading (75 pts)

• Using IDLE: 15 pts
• Python programs: 60 pts