1. LING 388: Computers and Language
Lecture 7

2. Today's Topics
Programming exercises (to be done in class)
Homework

3. Python https://docs.python.org/3/tutorial/introduction.html
We have covered:
Numbers
Strings (indexing, slices)
Lists (stacks, queues – see deques)
Sets
Dictionaries
Ranges

4. Exercise 1
Enter this (1st paragraph in "Alice's Adventures in Wonderland" by Lewis Carroll) into Python:
paragraph1 = 'Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do. Once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, "and what is the use of a book," thought Alice, "without pictures or conversations?"'
len(paragraph1) counts what?
What does paragraph1.split() do?
Store the result of split into a variable paragraph2
len(paragraph2) counts what?
Calculate the average number of characters per word

5. Exercise 2 Write a for loop to print each word on a separate line
paragraph2
['Alice', 'was', 'beginning', 'to', 'get', 'very', 'tired', 'of', 'sitting', 'by', 'her', 'sister', 'on', 'the', 'bank,', 'and', 'of', 'having', 'nothing', 'to', 'do.', 'Once', 'or', 'twice', 'she', 'had', 'peeped', 'into', 'the', 'book', 'her', 'sister', 'was', 'reading,', 'but', 'it', 'had', 'no', 'pictures', 'or', 'conversations', 'in', 'it,', '"and', 'what', 'is', 'the', 'use', 'of', 'a', 'book,"', 'thought', 'Alice,', '"without', 'pictures', 'or', 'conversations?"']
Write a for loop to print each word on a separate line
Notice some words end in punctuation, e.g. bank, or do. or book,"
Notice some words begin in punctuation, e.g. "and or "without. Try the following:
import re
word = 'conversations?"'
re.sub("[?\"'.]","",word)
Write a for loop to print the each word of paragraph2 (with punctuation deleted) on a separate line

6. Exercise 2 Enter this: What does this kind of for loop do?
[x.lower() for x in paragraph2]
[re.sub("[?\"'.]","",x) for x in paragraph2]
What does this kind of for loop do?
(It's called a list comprehension.)

7. Exercise 2: Examples
>>>[x.lower() for x in paragraph2] ['alice', 'was', 'beginning', 'to', 'get', 'very', 'tired', 'of', 'sitting', 'by', 'her', 'sister', 'on', 'the', 'bank,', 'and', 'of', 'having', 'nothing', 'to', 'do.', 'once', 'or', 'twice', 'she', 'had', 'peeped', 'into', 'the', 'book', 'her', 'sister', 'was', 'reading,', 'but', 'it', 'had', 'no', 'pictures', 'or', 'conversations', 'in', 'it,', '"and', 'what', 'is', 'the', 'use', 'of', 'a', 'book,"', 'thought', 'alice,', '"without', 'pictures', 'or', 'conversations?"'] >>>paragraph3 = [x.lower() for x in paragraph2] >>>paragraph3 >>>[re.sub("[,.?'\"]", "", x) for x in paragraph3] ['alice', 'was', 'beginning', 'to', 'get', 'very', 'tired', 'of', 'sitting', 'by', 'her', 'sister', 'on', 'the', 'bank', 'and', 'of', 'having', 'nothing', 'to', 'do', 'once', 'or', 'twice', 'she', 'had', 'peeped', 'into', 'the', 'book', 'her', 'sister', 'was', 'reading', 'but', 'it', 'had', 'no', 'pictures', 'or', 'conversations', 'in', 'it', 'and', 'what', 'is', 'the', 'use', 'of', 'a', 'book', 'thought', 'alice', 'without', 'pictures', 'or', 'conversations'] >>>[re.sub("[.,?'\"]", "",x.lower()) for x in paragraph2] >>>[re.sub("[.,?'\"]", "",x).lower() for x in paragraph2] >>>[re.sub("[.,?'\"]", "",x) for x.lower() in paragraph2] File "<stdin>", line 1 SyntaxError: can't assign to function call

8. Exercise 3
Enter this:
from collections import Counter
c = Counter()
c['alice'] += 1
c['a'] += 1 c
c.most_common()
See also

9. Homework 4 Starting with:
paragraph1 = 'Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do. Once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, "and what is the use of a book," thought Alice, "without pictures or conversations?"'
and using what you've learnt in Exercises 1–3, write Python code that builds a frequency table for words in paragraph1
Use the most_common() method to print your table
Submit your python console (cut and paste or screen snapshot) showing your work

10. Homework 4 Submit to TA Patricia Lee by next Wednesday (by midnight)
One PDF file only!