Python Program to check for balanced parentheses in an expression using stack class.

Parentheses_Balancer.py

'''
  Python Program to check for balanced parentheses in an expression using stack class.
  Given an expression as string comprising of opening and closing characters
  of parentheses - (), curly braces - {} and square brackets - [], we need to 
  check whether symbols are balanced or not. 
'''
from collections import deque                       # importing "double-ended queue"


class Stack:                                        # class for making a stack
    def __init__(self):                             # constructor
        self.control = deque()                      # initializing class object as a deque

    def push(self, value):                          # function for appending stack
        self.control.append(value)

    def pop(self):                                  # function to pop out latest value
        return self.control.pop()

    def size(self):                                 # returns the size of stack
        return len(self.control)

    def is_empty(self):                             # returns if stack is empty or not
        return len(self.control) == 0

    def show(self):                                 # pops whole stack and prints it
        for x in range(len(self.control)):
            print("'", end="")
            print(self.control.pop(), end="")
            print("'", end=",")


def parentheses_check(exp):                         # function for balancing parentheses
    stack = Stack()
    brackets = {'(': ')', '[': ']', '{': '}'}       # dict for storing brackets
    for i in exp:                                   # loop to iterate over string
        if i in brackets.keys():                    # check if it's opening bracket
            stack.push(i)                           # append to stack
        elif i in brackets.values():                # check if it's closing bracket
            popped = ""
            if not stack.is_empty():
                popped = stack.pop()
            """
                Below if condition checks following conditions:-
                    (if encountered closing bracket first) or (if it is not the pair of popped bracket)
            """
            if (stack.is_empty() and popped == "") or (i != brackets.get(popped)):
                print("Not Balanced!\nError: No opening brackets was found for: ", end="")
                print("'", end="")
                print(i, end="")
                print("'")
                return
    if stack.is_empty():                            # nothing in stack means all is well/balanced ;)
        print("All Balanced! You are good to go.")
    else:
        print("Not Balanced!\nError: No closing brackets were found for: ", end="")
        stack.show()


parentheses_check("{[(a+b)*c]/d}")                  # parsing a string value (expression) for balance check