issues they could instead convert the entry' text to number and do real mathbut python does all the work automatically when expression strings are run raw also note that the buttons added by these scripts simply operate on the current value in the entry fieldimmediately that' not quite the same as expression operators applied with the stacks evaluator (additional customizations are needed to make them true operatorsstillthese buttons prove the point these scripts are out to make--they use pycalc as componentboth from the outside and from below finallyto test both of the extended calculator classesas well as pycalc configuration optionsthe script in example - puts up four distinct calculator windows (this is the script run by pydemosexample - pp \lang\calculator\calculator_plusplus py #!/usr/local/bin/python ""demo all calculator flavors at once each is distinct calculator object and window ""from tkinter import tkbuttontoplevel import calculatorcalculator_plus_extcalculator_plus_emb root=tk(calculator calcgui(toplevel()calculator calcgui(toplevel()fg='white'bg='purple'calculator_plus_ext calcguiplus(toplevel()fg='gold'bg='black'calculator_plus_emb calcguiplus(fg='black'bg='red'button(roottext='quit calcs'command=root quitpack(root mainloop(figure - shows the result--four independent calculators in top-level windows within the same process the two windows on the right represent specialized reuses of pycalc as componentand the help dialog appears in the lower right although it may not be obvious in this bookall four use different color schemescalculator classes accept color and font configuration options and pass them down the call chain as needed as we learned earlierthese calculators could also be run as independent processes by spawning command lines with the launchmodes module we met in in factthat' how the pygadgets and pydemos launcher bars run calculatorsso see their code for more details and as alwaysread the code and experiment on your own for further enlightenmentthis is pythonafter all pycalca calculator program/object