Lab 2: String Operations, Functions, Modules, and Basic Loops

Goals

After the lab, you should know how to

  1. solve problems involving string operations
  2. format output nicely in Python
  3. utilize built-in and imported functions in Python
  4. solve basic looping problems in Python

Objective: Practice Using Linux

Set up for Lab 2

Create a directory called lab2 in your labs directory. Your programs and the output for this lab will all be saved in the lab2 directory.

Objective: Programming in Python

We'll practice writing several Python programs, each in their own text file. Name the files lab2.1.py through lab2.8.py.

Your programs will be graded on correctness, style, and how well you tested them. Make sure you adhere to the good development and testing practices we discussed in class. Your code should be readable and your output should be useful and well-formatted.

After you've developed a correct solution to each program, restart IDLE or close and reopen the IDLE "shell" by running the program again (using F5), demonstrate that the program works using several good test cases, and save the output to a file named lab2.x.out, where x is the problem number.

  1. (10 pts) Distributing Greatest Hits Albums. A supergroup is putting out their Greatest Hits album and needs to know how many cds their album requires. Bands like the Ramones can fit a lot more tracks on a cd than a band like Led Zeppelin.

    Write a program that takes the number of greatest hits and the size of the cds (in terms of the number of tracks) and determines how many cds are needed and how many tracks will have to wait for the next Greatest Hits album.

    This program determines the number of CDs in a Greatest Hits album.
    
    How many greatest hits/tracks do you have? 24
    How many tracks fit on a cd? 10
    
    Your album requires 2 cds
    4 tracks will have to wait for the next Greatest Hits album.
    

    Note: you may have some grammar issues in your output. We don't know how to fix that yet.

  2. (15 pts) [From Zelle, Chapter 3, Problem 3] Write a program that determines the total molecular weight of a molecule based on the number of hydrogen, carbon, and oxygen atoms it contains. You should use the following weights.

    AtomWeight
    (g/mol)
    H1.0079
    C12.011
    O15.9994

    You program should prompt the user for the number of atoms of each type and display the total weight with the appropriate units.

    Note that your program should use constants for the molecular weights of carbon, hydrogen, and oxygen. (Recall what the conventions are for naming constants. Why does it make sense to make these values constants?)

    Finally, modify your program so that it rounds the molecular weight to 3 decimal places (using a built-in function) and displays that number.

    A sample run is shown below:

       Enter number of Hydrogen atoms: 3
       Enter number of Carbon atoms: 2
       Enter number of Oxygen atoms: 1
    
       Weight of molecule is 43.045 g/mol
    
  3. (10 pts) Copy your program lab1.6.py that converted temperatures from Fahrenheit to Celcius. Modify the program so that it only displays temperatures to two decimal places.
  4. (15 pts) Write a program that creates a table of Olympic competition running distances in meters, kilometers, yards, and miles. The following distances should be used: 100 m, 200 m, 400 m, and 800 m.

    Note that 1 m = .001 km = 1.094 yds = .0006215 mi

    Do not try to use a for loop for this problem. (It's not straightforward. After you solve the problem, you can attempt a for loop. That's good programming.)

    Calculate and display the results, formatted in the following manner:

    
    Meters   Kilometers    Yards    Miles
    --------------------------------------
       100        0.100    109.4    0.062
       200        -----    -----    -----
       400        -----    -----    -----
       800        -----    -----    -----
    

    Note: Make sure your output looks exactly as above, but you will have all the converted values filled in.

  5. (12 pts) Write a program that calculates the area of a circle. Get the radius of the circle as input from the user. Use the most precise value of pi available to you, i.e., use the constant pi defined in the math module. Select a "reasonable" number of digits for precision in the result you display to the user.
  6. (12 pts) Using three variables (i, j, and result), assign them values to calculate and display result = i % j. Use assignment and print statements and a for loop to show the results of i % j, where i = 4 and j increases from 1 to 8. Example output (without the appropriate values filled in):
    4 % 1 = ?
    4 % 2 = ?
    ...
    
  7. (13 pts) Write a program that sums all the odd integers between 0 and 100 and prints the total using a loop. Define a constant to stop your loop.
  8. (13 pts) Using a for loop, draw a diagonal line that looks like:
    \
     \
      \
       \
        \
    

    Think about the pattern of what is getting printed. (Hint: a string operator may be useful.)

    After you have that working, have the user enter the size of the diagonal line and draw a line of the appropriate size.

Finishing up: What to turn in for this lab

  1. Copy your lab2 directory into the turnin directory. (Review the UNIX handout if you don't remember how to do that.)
  2. Cleanup: jEdit makes backup files and appends "~" to the name of your file. Delete any "~" files from your lab directory.
  3. Turn in your printed lab assignment, using the printLab.sh command:
    printLab.sh <labdirname>

    Again, you should probably print from the labs directory.

    View your file using the gv command.

    Print the file using the lpr command introduced in the first lab.

Labs are due at the beginning of Friday's class. You should hand in the printed copy at the beginning of class, and the electronic version should be in the turnin directory before 1:20 p.m. on Friday.

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

Grading (100 pts)