Modify the sentence$-$generator program of Case Study $5\mathrm{.}3$:

$$ METIS book: $9781337671019,$ page $150$

so that it inputs its vocabulary from a set of text files at startup. The filenames are nouns.txt$,$ verbs. txt$,$ articles.txt$,$ and prepositions.txt$.($Hint: Define a single new function, getWords. This function should expect a filename as an argument. The function should open an input file with this name, define a temporary list, read words from the file, and add them to the list. The function should then convert the list to a

tuple and return this tuple. Call the function with an actual filename to initialize each of the four variables for the vocabulary.$)$

Here's the python source code generator.py:

$"""$

Program: generator.py

Author: Ken

Generates and displays sentences using a simple grammar

and vocabulary. Words are chosen at random.

$"""$

import random

articles $=("$A$",$ "THE"$)$

nouns $=("$BOY$",$ "GIRL", "BAT", "BALL"$)$

verbs $=("$HIT$",$ "SAW", "LIKED"$)$

prepositions $=("$WITH$","$BY$")$

def sentence$()$:

$"""$Builds and returns a sentence."""

return nounPhrase$()+""+$ verbPhrase$()$

def nounPhrase$()$:

$"""$Builds and returns a noun phrase."""

return random.choice$($articles$)+""+$ random.choice$($nouns$)$

def verbPhrase$()$:

$"""$Builds and returns a verb phrase."""

return random.choice$($verbs$)+""+$ nounPhrase$()+""+\backslash$

prepositionalPhrase$()$

def prepositionalPhrase$()$:

$"""$Builds and returns a prepositional phrase."""

return random.choice$($prepositions$)+""+$ nounPhrase$()$

def main$()$:

$"""$Allows the user to input the number of sentences

to generate."""

number $=$ int$($input$("$Enter the number of sentences: $"))$

for count in range$($number$)$:

print$($sentence$())$

# The entry point for program execution

if $\_\_$name$\_\_=="\_\_$main$\_\_"$:

main$()$