Tkinter: AttributeError: NoneType object has no attribute <attribute name>

Question

I've created this simple GUI:

from tkinter import *

root = Tk()

def grabText(event):
    print(entryBox.get())    

entryBox = Entry(root, width=60).grid(row=2, column=1, sticky=W)

grabBtn = Button(root, text="Grab")
grabBtn.grid(row=8, column=1)
grabBtn.bind('<Button-1>', grabText)

root.mainloop()

I get the UI up and running. When I click on the Grab button, I get the following error on the console:

C:\Python> python.exe myFiles\testBed.py
Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python\lib\lib-tk\Tkinter.py", line 1403, in __call__
    return self.func(*args)
  File "myFiles\testBed.py", line 10, in grabText
    if entryBox.get().strip()=="":
AttributeError: 'NoneType' object has no attribute 'get'

Why is entryBox set to None ?

Answer 1

The grid , pack and place functions of the Entry object and of all other widgets returns None . In python when you do a().b() , the result of the expression is whatever b() returns, therefore Entry(...).grid(...) will return None .

You should split that on to two lines like this:

entryBox = Entry(root, width=60)
entryBox.grid(row=2, column=1, sticky=W)

That way you get your Entry reference stored in entryBox and it's laid out like you expect. This has a bonus side effect of making your layout easier to understand and maintain if you collect all of your grid and/or pack statements in blocks.

Answer 2

Change this line:

entryBox=Entry(root,width=60).grid(row=2, column=1,sticky=W)

into these two lines:

entryBox=Entry(root,width=60)
entryBox.grid(row=2, column=1,sticky=W)

Just as you already correctly do for grabBtn !

Answer 3

Alternative solution for Python3.8+ versions that allows to put all of this in one line using the walrus operator :

(entryBox := Entry(root, width=60)).grid(row=2, column=1, sticky=W)

Now entryBox will refer to the Entry widget and also get packed.

For characters per line management I can suggest something like this:

(var := Button(
    text='fine', command=some_func, width=20, height=15, activebackground='grey'
)).grid(row=0, column=0, columnspan=0, rowspan=0, sticky='news')

But at that point might as well just do this "normally" (as suggested by other answers)

Sources:

• PEP 572 -- Assignment Expressions
• IMO great video explanation about walrus operator

Answer 4

For entryBox.get() to access get() method you need Entry object but Entry(root, width=60).grid(row=2, column=1, sticky=W) returns None.

entryBox = Entry(root, width=60) creates a new Entry Object.

Moreover, you won't need entryBox = entryBox.grid(row=2, column=1, sticky=W) as it will rewrite entryBox with None

---

Just replace entryBox = entryBox.grid(row=2, column=1, sticky=W) with

entryBox = Entry(root, width=60)
entryBox.grid(row=2, column=1, sticky=W)

Answer 5

Tkinter does not allow the definition of a widget to be put in the same line as .grid() or .pack() . instead of putting entryBox = Entry(root, width=60).grid(row=2, column=1, sticky=W) ,

you should put:

entryBox = Entry(root, width=60)
entryBox.grid(row=2, column=1, sticky=W)

This is necessary due to the way which the Tkinter module is programmed.