I am trying to follow along in the book Python Programming for Kids. I am working with a group of neighborhood kids and to reduce the cost we are using the Raspberry Pi as our computer. I am a Windows guy and the GUI builder of choice for me is WxPython. I am trying to get ready for next weeks class and have run into a problem. I have entered the code below
from tkinter import *
tk = Tk()
btn = Button(tk,text = 'click me')
btn.pack()
according to the book the second line is supposed to create a window (frame I think in the Wx world) and the third line defines a button object and the fourth inserts it in the window.
However, this is not working - the tk window is not displayed nor is there a button on the screen and I have not been able to figure out why. tkinter is imported and the tk object has lots of methods/properties visible when I type dir(tk) so I know that we have tkinter on the Pi's.
Again, after entering this code nothing visible happens. I deleted the code relating to creating the button and still nothing happens so I am not sure where to start diagnosing the issue I have Googled for information and found nothing useful
Any insight would be appreciated.
I did ask this question on superuser but there is no Tkinter tag so . . .
humm do I need a
tk.pack()
statement - I will report back.
No, you do not need tk.pack(). What you do need is start the event loop. The event loop, as it's name suggests, is a loop that processes events. Everything in Tkinter happens as a response an event, including the actual drawing of a widget or window on the screen.
As the last line in your file, add the following:
tk.mainloop()
I encourage you to not do the import the way you are doing. I know a lot of tkinter tutorials do it that way, but it's a bad thing to do. Instead, do it like this:
import tkinter as tk
root = tk.Tk()
btn = tk.Button(root, text='click me')
btn.pack()
root.mainloop()
It requires typing three extra characters for every widget, but in exchange you get code that is easier to maintain over time.
PEP8 is the official python style guide, and it explicitly recommends against wildcard imports:
Wildcard imports (from import *) should be avoided, as they make it unclear which names are present in the namespace, confusing both readers and many automated tools. There is one defensible use case for a wildcard import, which is to republish an internal interface as part of a public API (for example, overwriting a pure Python implementation of an interface with the definitions from an optional accelerator module and exactly which definitions will be overwritten isn't known in advance).
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