[Tutor] A little math and Python: rpn

[Gregor Lingl]

... or would you prefer this approach?

class RPN_Tree:
   def __init__(self, rpnlist):
       if len(rpnlist) == 1:
           self.node = rpnlist[0]
           self.left = None
           self.right = None
       else:
           self.node = rpnlist[-1]
           if rpnlist[-2] in ["+","-","*","/"]:
               self.left = RPN_Tree(rpnlist[0:1])
               self.right = RPN_Tree(rpnlist[1:-1])
           else:
               self.left = RPN_Tree(rpnlist[:-2])
               self.right = RPN_Tree(rpnlist[-2:-1])
             
def evalTree(rpntree):
   if rpntree.node not in ["+","-","*","/"]:
       return rpntree.node
   else:
       return str(eval(evalTree(rpntree.left) + rpntree.node + 
evalTree(rpntree.right)))

def rpn(st):
   return evalTree(RPN_Tree(st.split()))

Gregor