python object is NoneType even after declaring as global: ttk textbox

[Peter Otten]

emagnun wrote:

> I have a very simple script that retrieves the value from a text box upon
> click of a checkButton. But in click event, I'm receiving text box object
> as NoneType even after setting it as global. Pls help.
> 
> Output: !!ERROR!! Tag is None
> 
> ########### Source Code ###########
> from tkinter import *
> from tkinter import ttk
> import os
> 
> def submitData():
>     global tag
>     global tagBox

You do not need the global declaration for tagBox as you do not rebind that 
name.

>     if (tagBox is not None):
>         tag = tagBox.get("1.0","end-1c")
>         print ("!!SUCESS!! tag -->", tag)
>     else:
>         print ("!!ERROR!! Tag is None")
> 
> gui = Tk()
> gui.title("GUI")
> gui.geometry('250x300')
> 
> tag = "NA"
> tagBoxLabel = Label(gui, text = "Tag: ").grid(column=0, row=5, pady=30,
> sticky="EN") 
> tagBox = Text(gui, height=1, width=20).grid(column=1, row=5,
> pady=30, sticky="WN")

The grid() method always returns None. So tagBoxLabel, tagBox, and 
submitButton are all bound to None.

To get a reference of the widget you need two steps:

# bind tagBox
tagBox = Text(...)

# define layout
tagBox.grid(...)
 
> submitButton = ttk.Button(gui, text="Submit", command=lambda:
> submitData()).grid(column=1, row=7)
> gui.mainloop()

Superfluous lambda alert: instead of 

lambda: submitData()

just write

submitData

, i. e.:

ttk.Button(..., command=submitData).grid()