Exercise_1.py

class myStack:
  # Please read sample.java file before starting.
  # Kindly include Time and Space complexity at top of each file
  
  # Time Complexity: O(1) for all operations
  # Space Complexity: O(n) where n is the number of elements in the stack

  def __init__(self):
    self.stack = []
    
  def isEmpty(self):
    return len(self.stack) == 0

  def push(self, item):
    self.stack.append(item)

  def pop(self):
    if self.isEmpty():
      return None
    return self.stack.pop()

  def peek(self):
    if self.isEmpty():
      return None
    return self.stack[-1]

  def size(self):
    return len(self.stack)

  def show(self):
    return self.stack


s = myStack()
s.push('1')
s.push('2')
print(s.pop())
print(s.show())