Multi tool use

Button switching using python (Tkinter)

What I'm trying to do is to switch buttons, basically.

When button 1 is pressed it gets destroyed and then button 2 launches.

I'm having an error, here's the code.

from Tkinter import *
root = Tk()
root.title('TEST')
def D1():
B.destroy()
Launch2()

def D2():
B2.destroy()
Launch1()

def Launch1():
B = Button (root, text = 'BUTTON 1', command = D1)
B.pack()


def Launch2():
B2 = Button (root, text = 'BUTTON 2', command = D2)
B2.pack()


Launch1()
mainloop()


Error :

Exception in Tkinter callback
Traceback (most recent call last):
File "C:Python27liblib-tkTkinter.py", line 1541, in __call__
return self.func(*args)
File "C:UsersyouseDesktopTkinter Testing GUI.py", line 5, in D1
B.destroy()
NameError: global name 'B' is not defined


B

2 Answers
2

Just add the lines, global B and global B2 to the code in the following way:

def Launch1():
global B # Make B a global variable
B = Button (root, text = 'BUTTON 1', command = D1)
B.pack()


def Launch2():
global B2 # Make B2 a global variable
B2 = Button (root, text = 'BUTTON 2', command = D2)
B2.pack()


The program now works perfectly for me.

The variable B in the function Launch1 is defined locally only in that function
The same is true for B2.
Hence the D1 function does not have access to B and D2 does not have access to B2.

You need to find a way to make function D see variable B
One solution is to create B outside the functions then use global B in the two functions launch1 and D - then do the same for B2
This is not a recommended solution, normally you would have a class defined that could hold B, B2 and the four functions then there would be no need for global variables

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