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Lab 2: Advanced Arithmetic and Definite Loops

Goals

After the lab, you should know how to

  1. more advanced arithmetic problems
  2. solve basic looping problems in Python

Objective: Review

Review the slides for today.

Objective: Set Up

Run runHelpClient &

Linux: Set up for Lab 2

  1. Create a directory called lab2 in your cs111 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 lab2.7.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.

You can use Python Visualizer to help you see what is happening in your program. This is the visualizer used in the text book.

  1. (10 pts) Copy problem 1 from lab 1 (lab1.1.py). Modify your program so that the program prompts the user for values of i and j. As will become common practice, demonstrate your program several times, with several different inputs to demonstrate that it works.
  2. (13 pts) Create a program that converts a given Fahrenheit temperature to Celsius. The formula to convert is C=5/9(F-32). Note that you cannot use this formula exactly in your program.

    Output should look similar to: 

    This program prints the Celsius temperature
given a Fahrenheit temperature.

Enter a Fahrenheit temperature: 70
70 degrees F is 21.111111111111111 degrees C

    Note: When you demonstrate this program, especially think about what are good test cases for this program. What answers do you know?

  3. (15 pts) Write a program that demonstrates the importance of operator precedence. Your program will get three integers from a user and assign them to the variables a, b, and c. Then, print the result of a Python expression that has no parentheses, using those three numbers. Then, show a different result from the same expression with one added pair of parentheses.

    Example output (with fake numbers--I'm not showing an equation): 

    Enter a: 12
Enter b: 34
Enter c: 5
The result of <print out your equation here> is 51.
The result of <print out your equation with parentheses here> is 15.
  4. (13 pts) Distributing Greatest Hits Albums. A band 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 those yet.

  5. (13 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 = 6 and j increases from 1 to 8. Example output (without the appropriate values filled in): 
    6 % 1 = ?
6 % 2 = ?
...
  6. (20) "Mind-blowing Math Trick Can Tell Your Age and Shoe Size" You may have heard about this silly trick. You probably didn't think about implementing it in a program, but you can!

    There are several steps, but they're all relatively simple to implement.

    1. Ask the user for their shoe size--don't allow them to use half sizes using a trick we learned--and their age.
    2. multiply the shoe size by five
    3. add 50 to that number
    4. take that total and multiply it by 20
    5. add 1,016 to that total
    6. subtract the year you were born

    The result: the first two numbers of the four-digit number are your shoe size and the last two numbers are your age. Extract those two numbers and present them to the user.

    Example Run:

     This program will figure out your shoe size and your age.
 Enter your shoe size (not half sizes): 9
 Enter the year you were born: 1996
 
 Working...
 Multiply shoe size by five
 45
 Add 50 to that number
 95
 Take that total and multiply it by 20
 1900
 Add 1016 to that total
 2916
 Subtract the year you were born
 920
 
 Your shoe size is 9
 Your age is 20
  7. Challenge Problem. (16) The Fibonacci sequence is 0, 1, 1, 2, 3, 5, 8, 13, ... The pattern is that the nth number is Fn=Fn-1 + Fn-2 for n greater than 1. The initial values of the sequence are defined as F0=0 and F1=1. Write a program that computes the first 15 numbers in the Fibonacci sequence.

    If you're having difficulty solving this problem, think about: How many times does this loop need to execute? What needs to be repeated? Try solving this problem by hand, calculating and writing out the results. You won't receive any help until we see that you have something written out. Hint: this is a modification of the accumulator design pattern.

    8. Finishing up: What to turn in for this lab

    1. Copy your lab2 directory into the turnin directory. If you have every thing set up correctly, you can do this by running turnin.sh lab2
    2. Clean up: jEdit makes backup files and appends "~" to the name of your file. Delete any "~" files from your lab directory.
    3. Go into your cs111 directory. Create the printable lab assignment, using the command:
      createPrintableLab <labname>
    4. View your file using the evince command. If there are issues with your printout, go back and fix them.
    5. Print the file using the lpr command introduced in the last 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 10 a.m. on Friday.

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

    Grading (100 pts)