old_contents: from src import var
  
  def parse_expr(expr):
      stack = []
      for term in expr:
          if not term in ('+', '-', '*', '/'):
              stack.append(var.get_var(term))
              
          elif term in ('+', '-', '/', '*'):
              operand = stack.pop()
              operand2 = stack.pop()
              if term == '+':
                  stack.append(operand1 + operand2)
                  
              elif term == '-':
                  stack.append(operand1 - operand2)
                  
              elif term == '*':
                  stack.append(operand1 * operand2)
                  
              elif term == '/':
                  stack.append(operand1 / operand2)
                  
      return stack[0]
  
new_contents: import src.var as essl
  
  def parse_expr(expr):
      stack = []
      for term in expr:
          if not term in ('+', '-', '*', '/'):
              stack.append(essl.get_var(term))
              
          elif term in ('+', '-', '/', '*'):
              operand = stack.pop()
              operand2 = stack.pop()
              if term == '+':
                  stack.append(operand1 + operand2)
                  
              elif term == '-':
                  stack.append(operand1 - operand2)
                  
              elif term == '*':
                  stack.append(operand1 * operand2)
                  
              elif term == '/':
                  stack.append(operand1 / operand2)
                  
      return stack[0]
  
subject: Update parse_expr.py