Wednesday 11/1

Slicing

What will be printed?

a = "Halloween"
print(a[2:3])
print(a[4:])
print(a[:4])
print(a[1:5:2])

Split and Join

What will be printed?

b = "These are the times that try men's souls"
print(b.split())
print(b.split("a"))
print("4".join(b.split("a")))

NLTK Package

• NLTK is a useful package for Natural Language Processing (NLP) tasks. For example:

  >>> import nltk
  >>> nltk.pos_tag(["tree"])
  [('tree', 'NN')]
  >>> sentence = "That squirrel is in a tree"
  >>> nltk.pos_tag(sentence.split())
  [('That', 'DT'),
   ('squirrel', 'NN'),
   ('is', 'VBZ'),
   ('in', 'IN'),
   ('a', 'DT'),
   ('tree', 'NN')]
  >>> sentence1 = "My dog will tree a squirrel"
  >>> nltk.pos_tag(sentence1.split())
   [('My', 'PRP$'),
    ('dog', 'NN'),
    ('will', 'MD'),
    ('tree', 'VB'),
    ('a', 'DT'),
    ('squirrel', 'NN')]
  

• Interesting example of processing Mary Shelly's Frankenstein (provided by Dr. Mayfield):

  from nltk.tokenize import word_tokenize
  from nltk.corpus import stopwords
  
  # Read the book into a string
  file = open("pg84.txt", encoding="utf-8-sig")
  text = file.read()
  
  # Count how many times each word occurs
  words = {}
  for word in word_tokenize(text):
      if word.isalpha():       # Ignore non-words
          word = word.lower()  # Ignore case
          # Update dictionary
          if word in words:
              words[word] += 1
          else:
              words[word] = 1
  
  # Remove stop words (like "the" and "you")
  stop_words = set(stopwords.words("english"))
  for word in sorted(words.keys()):
      if word in stop_words:
          count = words.pop(word)
          print(f"Removed {count} instances of {word}")
  
  # Display other frequently used words
  print()
  for word in sorted(words.keys()):
      count = words[word]
      if count >= 50:
          print(f"Found {count} instances of {word}")
  

Quiz Instructions

• Log into the desktop as student with no password.
• Log into Canvas.
• Wait until the instructor says to start before accessing Part 1.
• The quiz can be found in the "Modules" section of Canvas.
• The entire quiz has a 25 minute time limit.
• Part 1 (Conceptual):
  • You may not use Thonny (or any other resources) for Part 1.
• Part 2 (Coding):
  • You have unlimited submissions.
  • You do NOT need to provide docstrings.
  • The autograder will NOT check for PEP8 violations (though you should still use good style.)
  • You must use Thonny as your editor.
  • You may not access any external web pages or other resources.