(self, stack)
return stack
Post order walk op tree and produce postfix stack.

        Arguments:
            stack (list): user shall give empty list like `list()`, then it's
                          used recursively to construct the post-order stack.
Post order walk op tree and produce postfix stack.
Post order walk op tree and produce postfix stack .
def traverse(self, stack):
        """
        Post order walk op tree and produce postfix stack.

        Arguments:
            stack (list): user shall give empty list like `list()`, then it's
                          used recursively to construct the post-order stack.
        """
        # Left
        if isinstance(self[1], OpTreeNode):
            self[1].traverse(stack)
        elif self[1] is not None:
            stack.append(self[1])

        # Right
        if isinstance(self[2], OpTreeNode):
            self[2].traverse(stack)
        elif self[2] is not None:
            stack.append(self[2])

        stack.append(self[0])

        return stack
def traverse ( self , stack ) : # Left if isinstance ( self [ 1 ] , OpTreeNode ) : self [ 1 ] . traverse ( stack ) elif self [ 1 ] is not None : stack . append ( self [ 1 ] ) # Right if isinstance ( self [ 2 ] , OpTreeNode ) : self [ 2 ] . traverse ( stack ) elif self [ 2 ] is not None : stack . append ( self [ 2 ] ) stack . append ( self [ 0 ] ) return stack