ValueError: <tkinter.OptionMenu object .!optionmenu> is not in list
The problem was that self.drop2 is an object of OptionMenu, not the value of it. To get the value returned by it, use the get() method on its variable defined (self.clicked2.get())
So it should be:
print(safeDis[chem.index(self.clicked2.get())])Hope it solved the error, do let me know if any more doubts
Cheers