Repaired exercise-3.4.py. pep8 suggestions as well as removed extraneous comments.
Completed Exercise 13.4. Modify programa to print out all words that are not in word list. Appears that this is too good. I have to make dummy text with nonsense words to see its behaviour. May be the case that the stripping of punctuation I did is too comprehensive.
Completed Exercise 13.5. Create a function called 'choose_from_hist', that takes a histogram and returns a random chosen with probability in proportion to frequency.
Code from book, 13.3, Word histogram. Found a problem with ordering of the functions, since 'process_line' should be before 'process_file'. More efficient than my solution, but will need to double check.
Added the patently inefficient 'random_word' function to randomly select a word from the book.
Completed Exercise 13.7. Write a program to implement algorithm specified on page 130.
Removed extraneous whitespace, made copyright line two lines to avoid running over 80 characters.