How to update button text on Tkinter python (button1 not defined error message)-CodePudding

I am trying to update the button text on a TKinter GUI (learning TKinter!) but am coming up against a small problem. I am getting a button1 is not defined. I am sure I am missing something stupid!

def toggleText():  
 if button1["text"] == "hi":
 button1["text"] = "bye"
else:
 button1["text"] = "hi"

def selection():
 button1 = Button(tab1, text="hi", command=toggleText, height=5, width=10)
 button1.grid(column=1, row=1, padx=10, pady=10)
 root.mainloop() 
selection()

HERE IS THE OUTPUT I GET:
if button1["text"] == "hi":
NameError: name 'button1' is not defined

CodePudding user response：

You have a couple of options, the easiest is to just use global to make button1 a global name which can be accessed anywhere, just make sure that you call toggleText after calling selection:

def selection():
    global button1
    button1 = Button(...)
    ...

The other option is to use function arguments (which is better practice in this case):

# make `toggleText` accept an argument for button:
def toggleText(btn):
    if btn['text'] == 'hi':
        btn['text'] = 'bye'
    ...


def selection():
    # use lambda to pass an argument and since it is a lambda name
    # `button1` can be not yet defined since `lambda` is not called immediately
    button1 = Button(..., command=lambda: toggleText(button1))
    ...

Also:
I strongly advise against using wildcard (*) when importing something, You should either import what You need, e.g. from module import Class1, func_1, var_2 and so on or import the whole module: import module then You can also use an alias: import module as md or sth like that, the point is that don't import everything unless You actually know what You are doing; name clashes are the issue.

I strongly suggest following PEP 8 - Style Guide for Python Code. Function and variable names should be in snake_case, class names in CapitalCase. Have two blank lines around function and class declarations. Object method definitions have one blank line around them.