new_contents: """Implementation of a stack in python."""
  
  
  class Stack:
      def __init__(self):
          self.items = []
  
      def push(self, item):
          """Add an item to the stack."""
          self.items.append(item)
  
      def pop(self):
          """Remove the most recent item from the stack."""
          if len(self.items) > 0:
              last = self.items[-1]
              del(self.items[-1])
              return last
          else:
              raise IndexError
  
      def peek(self):
          """Return the most recent item to be pushed to the stack."""
          return self.items[-1]
  
      def isEmpty(self):
          """Returns True if stack is empty ."""
          return not len(self.items) >= 1
  
      def size(self):
          """Return the size of the stack."""
          return len(self.items)
  
subject: Add python stack data structure.