How to prohibit the input of several operations and points in a row?

Question

Python

Hello!
I am writing a graphing calculator in python using Kivy.
My task at the moment is to prohibit the input of several operations or points in a row.
I somehow got to similar information, but it was explained simply to raise the flag when an operation or point is entered, and after the introduction of the operand, lower it. I'm a newbie so I don't understand what this means, please help!

Answer 1

enter a variable, for example has_dot = False
When pressing a dot, if not has_dot, set has_dot = True, draw a dot, otherwise, ignore the pressing.
Same with operators.