1. Fundamentals of Programming I A Sentence Generator
Computer Science 111
Fundamentals of Programming I
A Sentence Generator

2. Application: Generate Sentences
Given a vocabulary and grammar rules, one can generate some random and perhaps rather silly sentences
Vocabulary - the set of words belonging to the parts of speech (nouns, verbs, articles, prepositions)
Grammar - the set of rules for building phrases in a sentence (noun phrase, verb phrase, prepositional phrase)

3. The Structure of a Sentence
noun phrase verb phrase
A sentence is a noun phrase followed by a verb phrase

4. The Structure of a Sentence
noun phrase verb phrase
article noun
A noun phrase is an article followed by a noun

5. The Structure of a Sentence
noun phrase verb phrase
article noun
the girl
Similar to the behavior of strings so far
Pick actual words for those parts of speech at random

6. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
the girl
Similar to the behavior of strings so far
A verb phrase is a verb followed by a noun phrase and a prepositional phrase

7. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
the girl threw
Similar to the behavior of strings so far
Pick a verb at random

8. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
article noun
the girl threw
Similar to the behavior of strings so far
Expand a noun phrase again

9. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
article noun
the girl threw the pie
Similar to the behavior of strings so far
Pick an article and a noun at random

10. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
article noun preposition noun phrase
the girl threw the pie
Similar to the behavior of strings so far
A prepositional phrase is a preposition followed by a noun phrase

11. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
article noun preposition noun phrase
the girl threw the pie at
Similar to the behavior of strings so far
Pick a preposition at random

12. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
article noun preposition noun phrase
article noun
the girl threw the pie at
Similar to the behavior of strings so far
Expand another noun phrase

13. The Structure of a Sentence
noun phrase verb phrase
article noun verb noun phrase prepositional phrase
article noun preposition noun phrase
article noun
the girl threw the pie at a boy
Similar to the behavior of strings so far
More random words from the parts of speech

14. Representing the Vocabulary
nouns = ['bat', 'boy', 'girl', 'dog', 'cat', 'chair',
'fence', 'table', 'computer', 'cake', 'field’, 'pie']
verbs = ['hit', 'threw', 'pushed', 'ate', 'dragged', 'jumped']
prepositions = ['with', 'to', 'from', 'on', 'below',
'above', 'beside', 'at']
articles = ['a', 'the']
Use a list of words for each part of speech (lexical category)

15. Picking a Word at Random
nouns = ['bat', 'boy', 'girl', 'dog', 'cat', 'chair',
'fence', 'table', 'computer', 'cake', 'field’, 'pie']
verbs = ['hit', 'threw', 'pushed', 'ate', 'dragged', 'jumped']
prepositions = ['with', 'to', 'from', 'on', 'below',
'above', 'beside', 'at']
articles = ['a', 'the']
import random
print(random.choice(verbs)) # Prints a randomly chosen verb
The random module includes functions to select numbers, sequence elements, etc., at random

16. Grammar Rules A sentence is a noun phrase followed by a verb phrase
sentence = nounphrase verbphrase
nounphrase = article noun
verbphrase = verb nounphrase prepositionalphrase
preopositonalphrase = preposition nounphrase
A sentence is a noun phrase followed by a verb phrase
Etc., etc.

17. Define a Function for Each Rule
# sentence = nounphrase verbphrase
def sentence():
return nounphrase() + ' ' + verbphrase()
Each function builds and returns a string that is an instance of the phrase
Separate phrases and words with a space

18. Define a Function for Each Rule
# sentence = nounphrase verbphrase
def sentence():
return nounphrase() + verbphrase()
# nounphrase = article noun
def nounphrase():
return random.choice(articles) + ' ' + random.choice(nouns)
When a part of speech is reached, select an instance at random from the relevant list

19. Call sentence() to Try It Out
# sentence = nounphrase verbphrase
def sentence():
return nounphrase() + verbphrase()
# nounphrase = article noun
def nounphrase():
return random.choice(articles) + ' ' + random.choice(nouns) …
for x in range(10): print(sentence()) # Display 10 sentences
You can also generate examples of the other phrases by calling their functions

20. Continue reading Chapter 5 on dictionaries
For Monday
Continue reading Chapter 5
on dictionaries