Question 1: Emulate the stack behaviour using the list data structure

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Question 1:

Emulate the stack behaviour using the list data structure.

a) Complete the methods of the following Stack class according to their description

 

 

 

 

class Stack:
  def __init__(self):
    """ Initialize a new stack """
    self.elements = []
  def push(self, new_item):
    """ Append the new item to the stack """
    ## CODE HERE ###
  def pop(self):
    """ Remove and return the last item from the stack """
    ## CODE HERE ###
  def size(self):
    """ Return the total number of elements in the stack """
    ## CODE HERE ###
  def is_empty(self):
    """ Return True if the stack is empty and False if it is not empty """
    ## CODE HERE ###
  def peek(self):
    """ Return the element at the top of the stack or return None if the stack is empty """
    ## CODE HERE ###

 

 

b) Use the Stack class that you defined in Q3a to complete the code of the is_valid() function, which checks whether the order of the brackets of an arithmetic expression is correct. Some examples are given below:

 

 

 

 

exp1 = "(2+3)+(1-5)" # True
exp2 = "((3*2))*(7/3))" # False
exp3 = "(3*5))]" # False

 

 

 

 

 

def is_valid(exp):
  """ Check the order of the brackets
      Returns True or False
  """
  opening = ['(', '[', '{']
  closing = [')', ']', '}']
  ## CODE HERE ##
  return ## CODE HERE ##
  
is_valid(exp1)
is_valid(exp2)
is_valid(exp3)

 

 

c) Use the Stack class that you defined in Q3a to complete the code of the count_pairs() function, which returns the number of the valid bracket pairs of an arithmetic expression. Some examples are given below:

 

 

 

 

exp1 = "(2+3)+(1-5)" # 2 pairs
exp2 = "((([()])))" # 5 pairs
exp3 = "[([])" # 2 pairs

 

 

 

 

 

def count_pairs(exp):
  """ Count the valid number of brackets
      Returns the total number of valid brackets in the string
  """
  opening = ['(', '[', '{']
  closing = [')', ']', '}']
  ## CODE HERE ##
  return ## CODE HERE ##
count_pairs(exp1)
count_pairs(exp2)
count_pairs(exp3)

 

 

Question 2:

According to each method's documentation, complete the code of the TextProcessor class and its subclass TextAnalyzer.

class TextProcessor: def __init__(self, text): self.text = text def setStopWords(): ''' set stop words as recieved in the parameters ''' ## CODE HERE ## def getStopWords(): ''' return stop words ''' ## CODE HERE ## def getUniqWords(self): return set(self.__text.split()) def getFilteredText(self): ''' remove filter words from the text return filtered text ''' ## CODE HERE ## class TextAnalyzer: def __init__(): ''' Construct the class ''' ## CODE HERE ## def getWordFrequency(): ''' Call the getFilteredText() method Create a dictionary of words key = word and value= frequency return the dictionary ''' ## CODE HERE ##

Verify the correctness of your code using the following steps:

1. Instantiate the TextAnalyzer class by creating an object called ta as follows:

ta = TextAnalyzer("a quick brown fox " +

"a quick brown fox jumps " +

"a quick brown fox jumps over " +

"a quick brown fox jumps over the " +

"a quick brown fox jumps over the lazy " +

"a quick brown fox jumps over the lazy dog")

2.Assign a list of stop words using the setStopWords() method: ta.setStopWords(['a', 'the'])

3.Count the occurrences of each word using the getWordFrequency() method: ta.getWordFrequency()

4.The output should be as follows {'quick': 6, 'brown': 6, 'fox': 6, 'jumps': 5, 'over': 4, 'lazy': 2, 'dog': 1}}

(ONLY QUESTION 2 is required to answer)