Save user input from tkinter to a variable and check its content

Question

I have written a script simulating a card game in Python where the user decides how many cards and how many piles of cards they want to play with. This input is controlled by following code where boundary_1 and boundary_2 give upper and lower limit in an integer interval and message is the user input:

def input_check(boundary_1, message, boundary_2): 
    run = True
    while run:
        try:
            user_input =int(input(message))   
            if boundary_1 <= user_input <= boundary_2:

                run = False
                return user_input
            else:
                print ("Incorrect Value, try again!")
                run = True
        except ValueError:
            print ("Incorrect Value, try again!")

I now want to try and make a GUI out of this card game using tkinter and I would therefore like to know if there's any way to save the user's input to a variable that could be sent into the input_check() function above? I've read through some tutorials on tkinter and found the following code:

def printtext():
    global e
    string = e.get() 
    text.insert(INSERT, string)   

from tkinter import *
root = Tk()
root.title('Name')
text = Text(root)
e = Entry(root) 
e.pack()
e.focus_set()
b = Button(root,text='okay',command=printtext)
text.pack()
b.pack(side='bottom')
root.mainloop()

The following code simply prints the user's input in the Textbox, what I need is the user's input being checked by my input_check() and then have an error message printed in the Textbox or the input saved to a variable for further use if it was approved. Is there any nice way to do this?

Many thanks in advance!

I'm very new to tkinter and have mostly been browsing around reading guides and examples of similar problems but I have tried a few approaches with little result. The main problem I've been having is that the input in the textbox doesn't seem to go anywhere. I've tried getting the input though the Entry widget and then defining the input to a variable through the .get() command but it doesn't return anything! — Nekroz, May 26 '15 at 17:56
If you want the contents of the text box to go somewhere, you have to tell them where to go... other than a local variable that gets thrown out as soon as the function ends. — TigerhawkT3, May 26 '15 at 18:22
That's what I tried to accomplish(not in the code written above) with the .get() command from the text box, wouldn't that be possible? — Nekroz, May 26 '15 at 18:33

score 2 · Accepted Answer · edited May 23 '17 at 11:51

2

The simplest solution is to make string global:

def printtext():
    global e
    global string
    string = e.get() 
    text.insert(INSERT, string)

When you do that, other parts of your code can now access the value in string.

This isn't the best solution, because excessive use of global variables makes a program hard to understand. The best solution is to take an object-oriented approach where you have an "application" object, and one of the attributes of that object would be something like "self.current_string".

For an example of how I recommend you structure your program, see https://stackoverflow.com/a/17470842/7432

edited May 23 '17 at 11:51

Community

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answered May 26 '15 at 18:13

Bryan Oakley

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Thank you very much for the quick answer! I want to refrain from using global variables as much as possible so I will try the suggested object-oriented approach. I found your answer to the other example really helpful as well, and when I started searching for posts about text input with classes I found http://stackoverflow.com/questions/15522336/text-input-in-tkinter which was a good example too if someone else is trying to solve the same problem! – Nekroz May 26 '15 at 18:31

Save user input from tkinter to a variable and check its content

1 Answers1