Problems by Eric Roberts, Nick Parlante, and the current CS106A staff.
This assignment will give you the opportunity to get lots of practice using strings as well as start to work with dictionaries (you'll get a lot more practice with dictionaries on assignments 6 and 7 as well). You can download the starter code for this project under the “Assignments” tab on the CS106A website. The starter project will provide Python files for you to write your programs in.
As usual, the assignment is broken up into two parts. The first part of the assignment focuses on some problems to give you practice writing functions with strings and dictionaries. The second part of the assignment is a longer program that uses strings to play a word guessing game (similar to the game Hangman, if you're familiar with that game). This is a complex task, but armed with the skills you've been honing, especially using decomposition, you’ll sail through.
A simple means for trying to compress text with many repeated characters is to use something known as run-length encoding. The idea is that rather than representing every character in a string explicitly, we instead simply have each character immediately followed by a digit which denotes how many times that character should be repeated. For example, the string 'B4' would represent the string 'BBBB' as the character B is to be repeated 4 times. Similarly, the string 'm1e2t1' would represent 'meet', as the character m is to be repeated 1 time, followed by the character e which is to be repeated 2 times, followed by the character t is to be repeated 1 time. Thus, the general format for run-length encoded strings is a series of pairs, where each pair contains a single character followed immediately by a single digit (1 through 9 only, the digit will never be 0). The digit denotes the number of consecutive occurrences of the character immediately before it in the encoded string.
Your job is to write a function named expand_encoded_string in the file encoded_string.py that takes as a parameter a called encoded, which is a string representing the run-length encoded text, and returns a string which is the expanded version of the text.
For example, if you call:
expand_encoded_string('B1o2k2e2p1e1r1!3')
your function should return the string:
'Bookkeeper!!!'
as the result.
Doctests are provided for you to test your function. Feel free to write additional doctests if you would like practice with that aspect of Python. Also, feel free to write any additional functions that may help you solve this problem. Tests for your function are provided in the main function included in the program.
Realizing that keeping track of credit card expenses is a particularly good use of your computer science skills, you decide to write a program that helps you track how much money you are spending at each store in a given month. Your program should read a data file (given by the constant named INPUT_FILE), which contains your credit card bill for a given month. Each line of the credit card bill represents one transaction. Each line starts with the date of the purchase, followed by a space, then the name of the store enclosed in square brackets, like so: [name] (you can assume no store names contain square bracket characters and store names also do not include the dollar sign ($) character), followed by a space, and then a dollar sign, and then the amount of the purchase (as an integer, since we assume here that transactions are just rounded to a whole dollar amount). A sample data file (bill1.txt) representing a credit card bill looks as follows:
File: bill1.txt
9/2/19 [Target] $12 9/21/19 [Stanford Bookstore] $102 9/30/19 [Jamba Juice] $5 10/7/19 [Target] $17 10/22/19 [Jamba Juice] $8 10/28/19 [Target] $45
In the file credit_card_total.py, you should write a program reads such a credit card bill file and prints to the screen the total amount that was purchased at each store on the bill. For example, given the input file bill1.txt (above), your program should print the output:
Target: $74 Stanford Bookstore: $102 Jamba Juice: $13
The output printed by your program should match the sample output as closely as possible, but you don't need to worry about the order in which the stores are printed. You can assume that the input file is properly formatted (as described above). Two sample input files (bill1.txt and bill2.txt) are provided in the assignment project folder to help you test your program. The output of your program using the file bill2.txt as input should be (again, you don't need to worry about the ordering of the stores in the output):
Shake Shack: $16 Grocery Hut: $293 Ace Hardware: $14 Joan's Fabric: $18 Nom Nom Nom: $12
Hint: using dictionaries would be a really good way to solve this problem!
For the second part of this assignment, your mission is to write a program that plays a word guessing game. This game is also some times called "Hangman", but we'll just call it "WordGuess" here. The WordGuess program is designed to give you some practice working with strings and files.
When the user plays WordGuess, the computer first selects a secret word at random from a list built into the program. The program then prints out a row of dashes—one for each letter in the secret word and asks the user to guess a letter. If the user guesses a letter that is in the word, the word is redisplayed with all instances of that letter shown in the correct positions, along with any letters correctly guessed on previous turns. If the letter does not appear in the word, the user is charged with an incorrect guess. The user keeps guessing letters until either (1) the user has correctly guessed all the letters in the word or (2) the user has made eight incorrect guesses. Two sample runs of the game are shown below (user input is shown in blue italics).
Sample Run 1:The word now looks like this: ----- You have 8 guesses left Type a single letter here, then press enter: a That guess is correct. The word now looks like this: -A--- You have 8 guesses left Type a single letter here, then press enter: q There are no Q's in the word The word now looks like this: -A--- You have 7 guesses left Type a single letter here, then press enter: p That guess is correct. The word now looks like this: -APP- You have 7 guesses left Type a single letter here, then press enter: C There are no C's in the word The word now looks like this: -APP- You have 6 guesses left Type a single letter here, then press enter: H That guess is correct. The word now looks like this: HAPP- You have 6 guesses left Type a single letter here, then press enter: y That guess is correct. Congratulations, the word is: HAPPY
Sample Run 2:The word now looks like this: ------ You have 8 guesses left Type a single letter here, then press enter: a There are no A's in the word The word now looks like this: ------ You have 7 guesses left Type a single letter here, then press enter: p That guess is correct. The word now looks like this: P----- You have 7 guesses left Type a single letter here, then press enter: H That guess is correct. The word now looks like this: P--H-- You have 7 guesses left Type a single letter here, then press enter: g There are no G's in the word The word now looks like this: P--H-- You have 6 guesses left Type a single letter here, then press enter: m There are no M's in the word The word now looks like this: P--H-- You have 5 guesses left Type a single letter here, then press enter: q There are no Q's in the word The word now looks like this: P--H-- You have 4 guesses left Type a single letter here, then press enter: d There are no D's in the word The word now looks like this: P--H-- You have 3 guesses left Type a single letter here, then press enter: L There are no L's in the word The word now looks like this: P--H-- You have 2 guesses left Type a single letter here, then press enter: E There are no E's in the word The word now looks like this: P--H-- You have 1 guesses left Type a single letter here, then press enter: r There are no R's in the word Sorry, you lost. The secret word was: PYTHON
In order to write the program that plays WordGuess, you should design and test your program in two parts. The first part consists of getting the interactive part of the game working with a fixed set of secret words (that are initially provided for you). The second part consists of replacing the supplied version of the secret word list with one that reads words from a file. The rest of this handout describes these two parts in more detail.
Note that your program only needs to be able to play the WordGuess game once through (i.e., the player guessing one word), but it should be pretty easy to extend your program to allow the player to play multiple rounds (i.e., guessing a word multiple times).
In the first milestone of this assignment, your job is to write a program that handles the user interaction component of the game. To solve the problem, your program must be able to:
For this part of the assignment, you will simply make use of a function that we’ve given you called get_word that returns a word (string) randomly chosen from a small list of words that will allow you to test your program. The initial code you are provided for the get_word function is only a temporary expedient to make it possible to code this part of the assignment. In Part II, you will reimplement the get_word function we’ve provided with one that reads a list of words from a data file in order to select the random word from a much larger set of possibilities.
The two sample runs shown previously should be sufficient to illustrate the basic operation of the game, but the following points may help to clarify a few issues:
The word now looks like this: ------ You have 8 guesses left Type a single letter here, then press enter: AA Guess should only be a single character. The word now looks like this: ------ You have 8 guesses left Type a single letter here, then press enter:
Milestone II is much easier than Milestone I and requires less than half a page of code. Your job in this part of the assignment is simply to re-implement the get_word function so that instead of being hard-coded to select from a meager list of three words, it reads a much larger word list from a file and returns a word from that list. The steps involved in this part of the assignment are as follows:
Note that nothing in the rest of the program should have to change in response to this change in the implementation of get_word. Insulating parts of a program from changes in other parts is a fundamental principle of good software design. Thus, in your implementation of the get_word, you should not be changing the parameters of this function.
As a side note, the file Lexicon.txt contains a very large list of words that can used to make the game more challenging to play, and the final version of your program should use that file for input. But to help you test this part of your program, we also provide a much smaller word list in the file TestLexicon.txt. You can feel free to use the TestLexicon.txt file to help you develop/debug your reimplementation of the get_word function, but make sure the final version of your program works properly with the full Lexicon.txt file.
Hint: remember to use the strip function when reading the file to avoid any nasty complications arising from newline characters at the end of lines.
Unicode still has not fully overtaken ASCII as the "default" standard for string representation in programming languages and computer systems. Suppose you are a software engineer implementing a website form meant to gather personal data such as names. Your boss expresses that your algorithm is only expected to work for ASCII-encoded strings, since supporting Unicode would require extra work and time. What would your response be? What representational harms might result from building a system that exclusively uses ASCII to represent strings?
There are many ways to extend the WordGuess game to make it more fun if you want. Of course, we encourage you to some up with yousr own ideas, but here are a few possibilites:
Once you've gotten all the parts of this assignment working, congratulations! You've now also got a fun game that you can play.
Make sure to submit all the python files for this assignment on Paperless. You should make sure to submit the files:
encoded_string.py credit_card_total.py word_guess.py ethics.txt
Additionally, in the Assignment 5 project folder, we have provided a file called extension.py that you can use if you want to write any extensions that you might want to make based on this assignment. The file doesn't contain any useful code to begin with. So, you only need to submit the extension.py file if you've written some sort of extension in that file that you'd like us to see.