Scrabble challenge

Project
Write a Scrabble cheater from scratch.

Goals

 * 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 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. An example invocation and output:

$ python scrabble.py ZAEFIEE 17 feeze 17 feaze 16 faze 15 fiz 15 fez 12 zee 12 zea 11 za 6 fie 6 fee 6 fae 5 if 5 fe 5 fa 5 ef 2 ee 2 ea 2 ai 2 ae

Resources

 * http://www.isc.ro/lists/sowpods.zip contains all words in the official SOWPODS word list, one word per line.
 * Here is a 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 1: construct a word list
Write the code to open and read the sowpods word file. Create a list, where each element is a word in the sowpods word file. Note that each line in the file ends in a newline, which you'll need to remove from the word.

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
Write the code to get the Scrabble rack (the letters available to make words) from the command line argument passed to your script. For example if your script were called `scrabble_cheater.py`, if you ran python scrabble_cheater.py RSTLNEI, RSTLNEI would be the rack.

Handle the case where a user forgets to supply a rack; in this case, print an error message saying they need to supply some letters, and then exit the program using the  function. Make sure you are consistent about capitalization: if your scores dictionary is lowercase, the letters supplied by the user need to be converted to lowercase at some point before you compare them.

Step 2 resources:   Command line argument parsing: http://docs.python.org/library/argparse.html#module-argparse.   Getting and checking the number of command line arguments: http://docs.python.org/library/sys.html.  Converting letters to lower case: http://docs.python.org/library/stdtypes.html#str.lower</li> </ul>

Step 3: find valid words
Write the code to find all words from the word list that are made of letters that are a subset of the rack letters. There are many ways to do this, but here's one way that is easy to reason about and is fast enough for our purposes: go through every word in the word list, and 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</tt> list. Make sure you handle repeat letters: once a letter from the rack has been used, it can't be used again.

Step 3 resources:   List manipulation: 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
Write the code to determine the Scrabble scores for each valid word, using the scores dictionary from above.

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

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

$ python scrabble.py Usage: scrabble.py [RACK]

$ python scrabble.py AAAaaaa 2 aa

$ python scrabble.py ZZAAEEI 22 zeze 21 ziz 12 zee 12 zea 11 za 3 aia 2 ee 2 ea 2 ai 2 ae 2 aa

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. Keep practicing!