Scrabble challenge

There's a huge leap between having learned the fundamentals of a programming language and being able to sit down at a blank text editor and implementing an idea from scratch.

The Boston Python Meetup would like to have events specifically for practicing "I sit down at a text editor with an idea -- now what?"

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 strip.

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 from a command line argument. Handle the case where a user forgets to supply a rack. 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.

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.  

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 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.  

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>

Step 5: printing
Write the code to print the valid words and their scores, in order by score.

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