O'Reilly Introduction to Python/Section 18

Goal #1: review the Scrabble cheater
We looked briefly at a Scrabble cheater in this video. To run it yourself, download these files to the same directory:


 * scrabble_cheater.py (the main program we run)
 * scrabble.py (the helper module)
 * sowpods.txt (the wordlist)

and then run scrabble_cheater.py with a rack, for example:

python scrabble_cheater.py ABCDEFG

Below, we also break down writing this Scrabble cheater into steps, as an example of how programmers tackle larger programming problems from scratch and so you can implement the cheater yourself if you want!

Goals for this project

 * practice breaking down a problem and solving it in Python from scratch
 * practice command line argument parsing
 * practice reading from files
 * practice working with dictionaries and for loops

Problem statement
Write a Python script that takes a Scrabble rack (the Scrabble letters you have to play) as a command-line argument and prints all valid Scrabble words that can be constructed from that rack, along with their Scrabble scores, sorted by score.

Here are an example invocation and output:

$ python scrabble_cheater.py ZAEFIEE 2 AE 2 AI 2 EA 2 EE 5 EF 5 FA 5 FE 5 IF 6 FAE 6 FEE 6 FIE 11 ZA 12 ZEA 12 ZEE 15 FEZ 15 FIZ 16 FAZE 17 FEAZE 17 FEEZE

Resources

 * sowpods.txt is a text file that contains all words in the official SOWPODS Scrabble word list, one word per line.
 * Here is a Python dictionary containing all letters and their Scrabble values:

scores = {"A": 1, "C": 3, "B": 3, "E": 1, "D": 2, "G": 2, "F": 4, "I": 1, "H": 4, "K": 5, "J": 8, "M": 3, "L": 1, "O": 1, "N": 1, "Q": 10, "P": 3, "S": 1, "R": 1, "U": 1, "T": 1, "W": 4, "V": 4, "Y": 4, "X": 8, "Z": 10}

Step 0: create a new Python file for the project
Since this Scrabble cheater is a bigger project, and something we'll want to be able to run over and over, we'll need to write it in a text file instead of interactively at the Python interpreter.

Open your text editor and create a new Python file. When you save it, give it the extension.

Step 1: construct a Python word list
We need to turn the words in the  file into a Python list.

To do this, write the code to open and read the contents of  line by line. As you go through each line in the file, build up a Python list, where each element in the list is a word from. Note that each line in the file ends in an invisible newline, which you'll need to remove from the word.

To check your work, use the  function to print the length of your Python word list. It should contain 267751 words.

Step 1 resources:   File input and output: http://docs.python.org/tutorial/inputoutput.html#reading-and-writing-files.   Stripping characters (like whitespace and newlines) from a string: http://docs.python.org/library/stdtypes.html#str.strip.  

Step 2: get the rack
The Scrabble rack (the letters available to make words) is provided to the script as a command line argument.

Write the code to get the Scrabble rack (the letters available to make words) from the command line argument passed to your script and save it in a variable.

To check your work, use the  function to print the Scrabble rack you've retrieved from the command line.

Step 2 resources:   Getting and checking the number of command line arguments: http://docs.python.org/library/sys.html.  

Step 3: find valid words
Next, we need to find all of the valid sowpods words that can be made up of the letters in the rack.

To do this, use a  loop to go through every word in the word list. For every letter in that word, see if that letter is contained in the rack. If it is, save the word in a valid_words list variable. Make sure you handle repeat letters: once a letter from the rack has been used, it can't be used again.

Hint: you will need to use a  loop inside of a   loop (the outer loop is for looping over the words, the inner loop is for looping over the letters in a word).

To check your work, use the  function to print   after the   loop.

Step 3 resources:   Using lists: http://docs.python.org/tutorial/datastructures.html#more-on-lists. </li>  for</tt> loops: http://docs.python.org/tutorial/controlflow.html#for-statements </li> </ul>

Step 4: scoring
Once we have a list of valid words, we need to get the Scrabble scores for each word.

To do this, use a  loop to go through each word in. For each word, use a counter to keep track of the score so far for the word. Then use another  loop to go through the word letter by letter; look up each letter in the   dictionary and add the point value for that letter to the counter.

To check your work, use the  function inside the   loop to print each word in   as well as its Scrabble value.

Step 4 resources:   Dictionaries: http://docs.python.org/tutorial/datastructures.html#dictionaries. </li> </ul>

Step 5: sorting
Now that we have the point values for each valid word, we need to sort them so it's easy to see what the highest-value words are.

Step 5 resources:   Lists, including sorting lists: http://docs.python.org/2/tutorial/datastructures.html#more-on-lists </li> </ul>

Checking your work
What happens when you run your script on the following inputs?

$ python scrabble_cheater.py AAA 2 AA

$ python scrabble_cheater.py ZZAAEEI 2 AA 2 AE 2 AI 2 EA 2 EE 3 AIA 11 ZE 12 ZEA 12 ZEE 22 ZEZE

Bonus challenge
Modify your script to handle blank tiles. Blank tiles have a score of 0 but can be used to represent any letter.

Congratulations!
You've implemented a substantial, useful script in Python from scratch that is perfect for cheating at Scrabble or Words with Friends. This is a huge accomplishment!



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