Question

Write a python program using the following requirements:

Create a class called Sentence which

• has a constructor that takes a sentence string as input.
  • The default value for the constructor should be an empty string
  • The sentence must be a private attribute in the class
• contains the following class methods:
  • get_all_words — Returns all the words in the sentence as a list
  • get_word — Returns only the word at a particular index in the sentence
    • Arguments: index
  • set_word — Changes the word at a given index in sentence to a new word
    • Arguments: index, new_word
    • Does not return anything
  • a str method — Returns the sentence as a string using the built in method

Include a unit test in an if __name__ block to test the class. Use assert to check for errors.

Unit Test Example:

• Set a sentence variable with a sentence of your choice
• Instantiate the Sentence object using the variable
• Test that get_all_words() correctly returns that sentence as a list
• Test that get_word(#) correctly returns the # word in the sentence
• Test that replace() actually changes a word in the sentence object
• Print the sentence before and after the word change using the built in str method

Answer 1

class Sentence:
        def __init__(self, sentence):
                self.__sentence = sentence

        def get_all_words(self):
                return self.__sentence.split()

        def get_word(self, index):
                return self.__sentence.split()[index]

        def replace(self, index, new_word):
                l = self.__sentence.split()
                l[index] = new_word
                self.__sentence = ' '.join(l)

        def __str__(self):
                return str(self.__sentence)


if __name__ == "__main__":
        s = "Hello, this is the sample test case."
        sentence = Sentence(s)

        # Testing get_all_words
        assert ["Hello,", "this", "is", "the", "sample", "test", "case."] == sentence.get_all_words()

        # Testing get_word(index)
        assert "Hello," == sentence.get_word(0) and "is" == sentence.get_word(2) and "test" == sentence.get_word(5)

        # Testing replace(index, new_word) along with print
        print("Before Replace:", sentence)
        sentence.replace(4, "new")
        assert str(sentence) == "Hello, this is the new test case."
        print("After Replace:", sentence)