Scrabble (tm) is a tile-based spelling game. Each tile has a single letter, and you draw 7 at random to start the game. The first person spells a word entirely using their own tiles, but ever other play in the game requires you to build off existing tiles on the board. We will write a program called scrabble.py that will find all the possible words you can make from all possible combinations a set of 7 Scrabble tiles using some other letter. That is, how many 3-letter words can you make using 2 of your own tiles plus an additional letter?

The program should respond to -h|--help for usage.

$ ./scrabble.py -h
usage: scrabble.py [-h] [-t str] [-l int] [-s int] [-w FILE]

Scrabble

optional arguments:
  -h, --help            show this help message and exit
  -t str, --tiles str   Input tiles (default: )
  -l int, --length int  Word length (default: 0)
  -s int, --seed int    Random seed (default: None)
  -w FILE, --wordlist FILE
                        Wordlist (default: /usr/share/dict/words)

As usual, your program needs to accept a -s|--seed argument to pass to random.seed for testing purpose. The -w|--wordlist is a standard dictionary file of English words but could be any text. All text should be converted to uppercase to match the letter on the tiles. The -l|--length option is to have your program only emit words of a particular length.

Lastly there is a -t|--tiles option to give the tiles on the command line. This is to help you cheat. When this is not present, you should randomly sample 7 tiles. The letters are not evenly distributed among the tiles. You will need to encode these letter frequencies into your program:

• Blank: 2
• A: 9
• B: 2
• C: 2
• D: 4
• E: 12
• F: 2
• G: 3
• H: 2
• I: 9
• J: 1
• K: 1
• L: 4
• M: 2
• N: 6
• O: 8
• P: 2
• Q: 1
• R: 6
• S: 4
• T: 6
• U: 4
• V: 2
• W: 2
• X: 1
• Y: 2
• Z: 1

When run in normal mode, it should select and show the tiles, then work through all combinations of 1 to 7 letters of the tiles and find all 2- to 8-letter words in the --wordlist that could be formed.

$ ./scrabble.py -s 1 > out
Tiles = "LNSHRAU"
     1: L => AL
     2: L => AL
     3: L => EL
     4: L => LA
$ tail -5 out
  1831: AHLRSU => RASHFUL
  1832: AHNRSU => RHAMNUS
  1833: AHNRSU => UNSHARP
  1834: AHLNRSU => RUSHLAND
  1835: AHLNRSU => UNLASHER

If given a --tiles argument, be sure it's only 7 characters long:

$ ./scrabble.py -t ABCDEFGHIJ
usage: scrabble.py [-h] [-t str] [-l int] [-s int] [-w FILE]
scrabble.py: error: --tiles "ABCDEFGHIJ" can only be 7 characters