In interactive mode, the last printed expression is assigned to the variable _. This means that when you are using Python as a desk calculator, it is somewhat easier to continue calculations. But, this variable should be treated as read-only by the user . DON '' @ you............................
In interactive mode, you can use _ instead of the previous calculation result, but you can't assign it, so that never produce an error, but in fact, a new variable is defined.
