Lab 7: Indefinite Loops, Strings, and ASCII

Staggered Extension

Problems 1-7 are due Friday, as usual.

Problems 8, 9, Extra Credit are due on Monday before class.

Goals

After the lab, you should be proficient at

using indefinite loops to solve problems
using escape sequences
using the ASCII representations of characters with built-in functions
formatting strings

Objective: Review

Review the slides for today's lab.

Objective: Set Up

Set up the help client:
runHelpClient
Create a directory for this lab.
Copy all the .py files in /csdept/courses/cs111/handouts/lab7/ into your lab7 directory.

Objective: Programming in Python

We'll practice writing several Python programs, each in their own text file.

Your programs will be graded on correctness, style, efficiency, 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 lab7_x.out, where x is the problem number.

(12) Previously, we wrote a program that displayed "Eureka!" or another message for certain values. This time, write a program that repeatedly prompts the user for a number until that number is between 500 and 1000, inclusive, at which point the program will print "Eureka!".
(25) Simulate a simple Craps game (without betting). Break the game into manageable pieces and build up. For example, make your program simulate rolling two dice (recall: you copied the game.py module at the beginning of the lab) and then test your program. Then, handle when the person first rolls a 2, 3, 7, 11, or 12. Then, handle the point.

The Rules
1. A player rolls two dice.
2. There are three possibilities:
  - 7 or 11 wins. If the total of the dice is 7 or 11, then the player wins.
  - 2, 3, or 12 loses. If the total of the dice is 2, 3, or 12, then the player loses.
  - Others become the point. If the total is any other number (4, 5, 6, 8, 9, 10), then this number becomes the point.
    The player keeps rolling until one of two things happen. Either the player makes the point and wins, or the player rolls a 7 and loses (craps out). Any number other than the point or 7 is of no consequence.
After the first roll, print a message that tells the player that they either won, lost, or which "point" they have to play for.
Example runs:
```
*** This program simulates Craps (without the betting) ***

You rolled a 11
Congratulations!  You win!
```
```
*** This program simulates Craps (without the betting) ***

You rolled a 6
The POINT is 6
Roll again!

You rolled 4
Roll again!

You rolled 6
Congratulations!  You win!
```
```
*** This program simulates Craps (without the betting) ***

You rolled a 10
The POINT is 10
Roll again!

You rolled 4
Roll again!

You rolled 9
Roll again!

You rolled 7
Sorry!  You crapped out.  Luckily, money wasn't involved.
```
(18) Write a function called stretchString that returns the single string (provided as a parameter) stretched by inserting periods between each letter. One period should appear after the first letter, two dots after the second letter, and n dots after the nth letter. (Recall good practices for writing functions.)
For example, if I call stretchString("cs"), the function should return "c.s..". If I call stretchString("cs111"), the function should return "c.s..1...1....1....."
Test that your function works using the test.testEqual function. Put these tests in a test function, as you did in previous labs.
After confirming that your function works, create a main function that prompts the user for input and displays the user's input stretched.
Example output:
```
This program stretches a word that you provide.
    
Enter your word: cs
The stretched word is c.s..
```
```
This program stretches a word that you provide.
    
Enter your word: monkeys
The stretched word is m.o..n...k....e.....y......s.......
```

Caesar Cipher

Pedagogical Overview: We're going to build up the Caesar cipher code in a couple of steps. By the end of the term, you should feel comfortable with breaking up a problem yourself. In the meantime, we'll go through a few examples of breaking up a program into components that are easier to solve. You can peek at the last Caesar Cipher Code problem to see where we're going.

A Caesar cipher is a simple substitution cipher based on the idea of shifting each letter of a text message a fixed number (called the key) of positions in the alphabet. Recall that the alphabet wraps around. For example, 'z' with a key of 5 is encoded as 'e'.

Rhetorical question: why is the limit on keys between -25 and +25?

(13) Write a function called encodeLetter that takes as parameters a lowercase letter and a key and returns the letter encoded. For example, if you call the function encodeLetter('a', 1), the function should return 'b'. Similarly, if you call the function encodeLetter('b', -1), the function should return 'a'.
As we've been doing, write the function and test it using the test.testEqual function in a function called testEncodeLetter. What are good test cases for this function?

No main or user input for this program... We're building up to that. No output for this program, unless you want me to see a bunch of "Pass" messages.
(13) Copy the previous program and add a function called encodeMessage that takes a message to encode and a key as parameters and returns the encoded message. For example, if you call encodeMessage("w and l", 1), the function should return "x boe m".
The function you created in the last problem will likely be helpful to call. (Read: you should call that function in this function.) You should NOT modify the function you wrote in the previous problem. You already know that's working, so don't modify that function.
Note that spaces will have to be handled specially.
As before, create a function that tests this function. What are good test cases for this function?

Still no main or user input for this program... We're building up to that. No output, unless you want to show all of your test cases pass.
(13) Copy the previous program and create your final Caesar Cipher program. The program will take as input a phrase to encode and a key and will display the encoded phrase. Your program should handle the error case where the user-supplied key is not in the valid range.
Your program can assume that messages only contain lowercase letters and spaces.
Give your neighbor a message to decode, along with the original key used to encode the message. Put your neighbor's name, the original message, and the decoded message in comments in your finished program, right under the high-level description. If others aren't around, decode this message, which I generated using the key 12: bkftaz ue yk rmhadufq bdasdmyyuzs xmzsgmsq Show your code decoding the message in your saved output.

Your program should produce the following interaction with the user:
```
This program encodes and decodes Ceasar ciphers.

Enter some text: i like the lions at the zoo
Enter an integer key (between -25 and + 25): 1
The encoded text is: j mjlf uif mjpot bu uif app 
```
```
This program encodes and decodes Ceasar ciphers.

Enter some text: j mjlf uif mjpot bu uif app 
Enter an integer key (between -25 and + 25): -1
The encoded text is: i like the lions at the zoo 
```
(10 pts) Using a for loop, draw a diagonal line that looks like:
```
\
 \
  \
   \
    \
```
Think about the pattern of what is getting printed.

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

(8 pts) Copy lab2/lab2.2.py into this directory and name it appropriately for this lab. Update the comment appropriately. Modify it such that the program always displays the money values to 2 decimal places. Note the change with the placement of the dollar sign.

Output should look like:

Bill amount in dollars: 55.34
Percent tip: 20
Number of people: 3

The tip is $11.07.
The total cost is $66.41.
The cost per person is $22.14.

Bill amount in dollars: 162.29
Percent tip: 15
Number of people: 8

The tip is $24.34.
The total cost is $186.63.
The cost per person is $23.33.

(18 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, 800 m, and 1600m.
Note that 1 m = .001 km = 1.094 yds = .0006215 mi

Calculate and display the results, formatted in the following manner:
```
Meters   Kilometers     Yards    Miles
---------------------------------------
   100        0.100     109.4    0.062
   200        -----     -----    -----
   400        -----     -----    -----
   800        -----     -----    -----
  1600        -----    ------    -----
```
Note: Make sure your output is formatted exactly as above except that you will have all the converted values filled in. Note the spacing of the columns, the justification of the columns, the precision, ...

Your final solution should not have a lot of repeated code. How can you solve this problem without repeated code?

You should not use a list to solve this problem.

Extra Credit

Vignere Cipher (up to 8 pts)

We can provide problem clarifications, but I'd like you to try to solve extra credit problems on your own.

Write a program that implements a Vigenere cipher. Name the Python file vignere_ec.py. You should be able to leverage your previous code to solve this problem. Some example output:

This program encodes Vignere ciphers.

Enter some text: the eagle flies at midnight
Enter a keyword: key

Encoded text: dlc iyqpc jjsiq er qgnrgqlr

"Best of" Simulator (up to 6 points)

Write a "best of" simulator that simulates two teams playing a "best of" series.

Copy your Championship/March Madness simulator from Lab 5 (problem 7) and name it simulator_ec.py. Keep most of the constants and your boolean function. Change the simulator so that it stops after a team has won the required number of games in the series. Have constants that represent the maximum number of games to play and the name of the series. Update the output accordingly. Some example output:

Play the Best of 7 Series in the World Series
--------------------------------------------------
Simulation 1 : Pirates wins
Simulation 2 : Orioles wins
Simulation 3 : Orioles wins
Simulation 4 : Orioles wins
Simulation 5 : Orioles wins
--------------------------------------------------
Orioles won the World Series 4 - 1

Play the Best of 5 Series in the Wild Card Playoff
--------------------------------------------------
Simulation 1 : Orioles wins
Simulation 2 : Pirates wins
Simulation 3 : Pirates wins
Simulation 4 : Orioles wins
Simulation 5 : Pirates wins
--------------------------------------------------
Pirates won the Wild Card Playoff 3 - 2

Finishing up: What to turn in for this lab

Problems 1-7 are due Friday. Problems 8, 9, Extra Credit are due on Monday before class.
Follow these steps for both the Friday and Monday deadlines.

Note that each command links to a page with more information about using the command.

Create the printable lab assignment, using the createPrintableLab command:
createPrintableLab <labdirname>
View your file using the evince command.
Submit your lab directory into your turnin directory.
Log out of your machine when you are done.

Problems 1-7 are due Friday. Problems 8, 9, Extra Credit are due on Monday before class.

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

Grading (130 pts)

Python programs: 130 pts; see above for breakdown