create One$-$Way linked list using python

First node will have the count of the number of nodes available in the linked list

$($excluding the first node$)$

initially the linked list will have $1$ node with value $"0"$indicating zero node.

The linked list will contain a mathematical expression given by the user during run$-$time.

Your program must do the following : Check the input expression for Brackets

$/$Parenthesis checking.

When the Brackets$/$Parenthesis checking is validated then convert the expression to its

equivalent post$-$fix expression.

Replace the given input linked list with the postfix linked list while maintaining the node count $($ first node $)$