def $\_$getPostfix$($self$,$ txt$)$:

$\text{'}\text{'}\text{'}$

$$ Required: $\_$getPostfix must create and use a Stack for expression processing

$>>>$ x$=$Calculator$()$

$>>>$ x$.\_$getPostfix$(\text{'}2^4\text{'})$

$\text{'}2\mathrm{.}04\mathrm{.}0^\text{'}$

$>>>$ x$.\_$getPostfix$(\text{'}2\text{'})$

$\text{'}2\mathrm{.}0\text{'}$

$>>>$ x$.\_$getPostfix$(\text{'}2\mathrm{.}1*5+3^2+1+4\mathrm{.}45\text{'})$

$\text{'}2\mathrm{.}15\mathrm{.}0*3\mathrm{.}02\mathrm{.}0^+1\mathrm{.}0+4\mathrm{.}45+\text{'}$

$>>>$ x$.\_$getPostfix$(\text{'}2*5\mathrm{.}34+3^2+1+4\text{'})$

$\text{'}2\mathrm{.}05\mathrm{.}34*3\mathrm{.}02\mathrm{.}0^+1\mathrm{.}0+4\mathrm{.}0+\text{'}$

$>>>$ x$.\_$getPostfix$(\text{'}2\mathrm{.}1*5+3^2+1+4\text{'})$

$\text{'}2\mathrm{.}15\mathrm{.}0*3\mathrm{.}02\mathrm{.}0^+1\mathrm{.}0+4\mathrm{.}0+\text{'}$

$>>>$ x$.\_$getPostfix$(\text{'}(\mathrm{.}5)\text{'})$

$\text{'}0\mathrm{.}5\text{'}$

$>>>$ x$.\_$getPostfix $(\text{'}((2))\text{'})$

$\text{'}2\mathrm{.}0\text{'}$

$>>>$ x$.\_$getPostfix $(\text{'}2*((5+-3)^2+(1+4))\text{'})$

$\text{'}2\mathrm{.}05\mathrm{.}0-3\mathrm{.}0+2\mathrm{.}0^1\mathrm{.}04\mathrm{.}0++*\text{'}$

$>>>$ x$.\_$getPostfix $(\text{'}(2*((5+3)^2+(1+4)))\text{'})$

$\text{'}2\mathrm{.}05\mathrm{.}03\mathrm{.}0+2\mathrm{.}0^1\mathrm{.}04\mathrm{.}0++*\text{'}$

$>>>$ x$.\_$getPostfix $(\text{'}((2*((5+3)^2+(1+4))))\text{'})$

$\text{'}2\mathrm{.}05\mathrm{.}03\mathrm{.}0+2\mathrm{.}0^1\mathrm{.}04\mathrm{.}0++*\text{'}$

$>>>$ x$.\_$getPostfix$(\text{'}2*(-5+3)^2+(1+4)\text{'})$

$\text{'}2\mathrm{.}0-5\mathrm{.}03\mathrm{.}0+2\mathrm{.}0^*1\mathrm{.}04\mathrm{.}0++\text{'}$

$$ # In invalid expressions, you might print an error message, adjust doctest accordingly

$$ # If you are veryfing the expression in calculate before passing to postfix, this cases are not necessary

$>>>$ x$.\_$getPostfix$(\text{'}2*5+3^+-2+1+4\text{'})$

$>>>$ x$.\_$getPostfix$(\text{'}2*5+3^*2+1+4\text{'})$

$>>>$ x$.\_$getPostfix$(\text{'}25\text{'})$

$>>>$ x$.\_$getPostfix$(\text{'}25+\text{'})$

$>>>$ x$.\_$getPostfix$(\text{'}2*(5+3)^2+(1+4\text{'})$

$>>>$ x$.\_$getPostfix$(\text{'}2*(5+3)^2+)1+4(\text{'})$

$>>>$ x$.\_$getPostfix$(\text{'}2*5\%+3^+-2+1+4\text{'})$

$\text{'}\text{'}\text{'}$

$$ # YOUR CODE STARTS HERE

$$ postfixStack $=$ Stack$()$# method must use postfixStack to compute the postfix expression

$$ pass