I am trying to use the invoke method of a ttk.Button, as shown at TkDocs (look at “The Command Callback”), but I keep getting this error:
AttributeError: ‘NoneType’ object has no attribute ‘invoke’
So, I tried this in the Interactive Shell:
ActivePython 3.1.1.2 (ActiveState Software Inc.) based on Python 3.1.1 (r311:74480, Aug 17 2009, 12:30:13) [MSC v.1500 32 bit (Intel)] on win32 >>> from tkinter import * >>> import tkinter.ttk as ttk >>> root = Tk() >>> button = ttk.Button(root, text="Test").grid(row=0, column=0) >>> print(button) None
Which shows that ttk.Button returns None.
Is ttk.Button meant to return None. And, if so, why does TkDocs say that there is an invoke method?
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Answer
No, you’re entirely wrong: your code does not show that ttk.Button
returns None
— it shows that the grid
method on the button object returns None
! Don’t you see that you’re calling .grid
on whatever it is that ttk.Button
returns (the button object), and it’s the result of that grid call that you’re assigning to “button”?!
So do it right instead…:
button = ttk.Button(root, text="Test") button.grid(row=0, column=0)
now you can print button
and of course the results will be very different!-)