Make App Pie
Training and Instructional Design
From Apple to Raspberry Pi: Why use a Tkinter Listbox?
As those who have followed this series over the last few weeks might have noted, I’ve racked my brain trying to get around the Tkinter Listbox. For those not familiar with the Tkinter Listbox, it’s a GUI widget which allow for selection from a list of items, but the items can only be one word long. I’ve wondered why they put it together so you can only use one word in the selection. It seems so totally useless. Now I think I figured it out.
I’ve been working on a camera application. The API I’m using has a lot of dictionaries to set modes on the camera. When making the UI for the camera I found why Tkinter was so interested in single word selections is dictionary keys.
In a new file add the following code:
from tkinter import *
METER_MODES = {'Auto':1,'Spot':2,'Matrix':4,'Backlit':8}
#controller
def meterModeSelected(event):
index = meterMode_listbox.curselection()
selection = meterMode_listbox.get(index[0])
modelabel.set(selection)
# a method to take a dictionary and return its keys as a space delimited string
def listboxlist(aDictionary):
x=""
for i in list(aDictionary):
x=x+i+" "
return x
#view
#make the window
root=Tk()
root.title('Camera demo #1')
#make the frame
frame = Frame(root)
frame.grid(row=0, column=0)
#label
modelabel = StringVar()
modelabel.set('Meter Modes')
label = Label(frame,textvariable = modelabel).grid(row=0, column=0)
#meter mode listbox
meterMode_list = StringVar()
meter_modes = listboxlist(METER_MODES) #extract a list as a string from the dictionary
meterMode_list.set(meter_modes)
meterMode_listbox = Listbox(frame,listvariable=meterMode_list, width = 10)
meterMode_listbox.grid(row = 1, column = 0)
meterMode_listbox.bind('',meterModeSelected)
#main loop
mainloop()
Line 3 sets up a dictionary, which we use in line 31 to call the function listboxlist in lines 10-14. Dictionaries when cast as lists make a list of the dictionary keys. This for loop changes the list into a string with spaces, exactly what Listbox uses.
In short, the Listbox is a quick way to select from a dictionary or list. It still isn’t what we need for Popper’s Penguins, but at least we know what the reason is for Listbox’s design.
Subscribe to A Slice of App Pie Newsletter
If you are making your own stuff, doing your own work and trying to sell it in the market, most advice isn't enough. You want it to work. You want to sell your works to those who most are touched by them. This newsletter is for you. I am one of those people like you, creative, independent and maybe a little bit crazy to the outside world. I'll talk about writing good apps for Apple platforms, the tools and API's to get there. Along the way I will show you how to become you best creative self. I will show you how to build and create, and make some money at it too.
Get exclusive content, new post notifications, tips and more in A Slice of App Pie.
