如何在 Python 中删除字符串的一部分

Question

I am coding a calculator. I decided to use 2 strings, one that is shown to the user on a screen, and one, that is for making the calculation. I now want to make a function that deletes everything on the screen. But now I have the problem, that the variable, that is used to perform the calculation, still has the value of the number inside of it. I wanted to ask, how I could remove that number. I also use a tkinter window, to show everything.

Here is the function, where I wanted to do that:

def clear_S(event):
    global Evaluation_T    #This gets shown
    global Evaluation_C    #This is for the calculation
    Evaluation_T = "                "
    renew_Label()          #Displays it to a 
    Evaluation_T = ""
    #Logic, to remove that from Evaluation_C

If you need any more information, please ask.

Answer 1

It's not how input and output work. When you print something, you print the value of that variable on STDOUT which is a stream file to connect your software with your terminal. What you're doing it like do a photocopy and edit the original copy expecting that the photocopy will be edited too. Have a look at Is there a way to clear your printed text in python? it should be what you were looking for.

EDIT: I misunderstand what you asked. There are different solutions: 1) If Evaluation_Text is always the end of Evaluation_C you can do:

Evaluation_C = Evaluation_C[:-len(Evaluation_Text)]

or

2) You can use replace with reverse string and do it only one time with:

Evaluation_C[::-1].replace(Evaluation_Text[::-1], 1)