{"id":3067,"date":"2019-08-20T08:31:45","date_gmt":"2019-08-20T06:31:45","guid":{"rendered":"https:\/\/pythonprogramming.altervista.org\/?p=3067"},"modified":"2019-08-22T13:25:52","modified_gmt":"2019-08-22T11:25:52","slug":"tkinter-and-listbox-1","status":"publish","type":"post","link":"https:\/\/pythonprogramming.altervista.org\/tkinter-and-listbox-1\/","title":{"rendered":"Tkinter and listbox – 1"},"content":{"rendered":"

Let’s talk again about listbox<\/strong>… and tkinter<\/strong>, some of my favourite topics. As I do sometimes want to revisit code to make some basic examples of possible use, sometimes suggested by question that someone makes.<\/p>\n

Create one or more listboxes with less code<\/h2>\n

Follow me in this live coding about listboxes and tkitner to see how you can use them writing less code. At the end of this live coding we will have 2 listboxes that will scroll in sync.<\/p>\n

In the first part we just create 2 listboxes in a frame and we populate them with random items (numbers). We use the pack method to organize the widgets on the window. The frame is a container that we use to give the app a better layout, being the pack() method easy to use, but very limited to center, left and right positioning.<\/p>\n

Importing stuff<\/h2>\n

We need tkinter and random (the second is just to fill the listboxes with random numbers).<\/p>\n

import tkinter as tk\r\nfrom random import randint<\/pre>\n
Window, title and dimensions<\/h2>\n
We… do what you can imagine reading the very intuitive code below:<\/p>\n
root = tk.Tk()\r\nroot.title(\"Listboxes in Sync\")\r\nroot.geometry(\"400x300+400+200\")<\/pre>\n
A function to use less code to create the listboxes<\/h2>\n
As we are going to create 2 listboxes, we create a ‘shortcut’ reusing this code twice:<\/p>\n
def def_listbox(): # => Listbox\r\n\tlb = tk.Listbox(frame1)\r\n\tlb.pack(side=\"left\", expand=1, fill=tk.BOTH)\r\n\r\n\tfor n in range(49):\r\n\t\trnd = str(randint(1,100))\r\n\t\tlb.insert(tk.END, rnd)\r\n\treturn lb<\/pre>\n
We created the listbox from an instance of Listbox (tk is the tkinter module, to have access to the module we have to write tk then a dot . and the the name of the class or function or attribute coming from the module; PS: we gave to tkinter the name of tk in the import line above).<\/p>\n
This function returns a lb istance of Listbox. So each time we call this function a Listbox is created. To create more Listbox and have the chance to work on them you have to memorize the call to this function in a label like this:<\/p>\n
lb1 = def_listbox()<\/pre>\n
If you want another Listbox, you just:<\/p>\n
lb2 = def_listbox()<\/pre>\n
If we didn’t wrote the function, we should have written the same stuff in the function twice. So, we saved space and simplified the readability of the code (and also his mantainance).<\/p>\n
We need to create the frame in wich the listboxes are contained (it is the argument frame1 in the first line of code of the function above.<\/p>\n
The frame widget must be created before the listbox object, otherwise the interpreter will give us an error.<\/p>\n
frame1 = tk.Frame(root)\r\nframe1.pack(expand=1, fill=tk.BOTH)<\/pre>\n
The whole code for listboxes in tkinter<\/h2>\n
So, we’re done, add the mainloop and run this code:<\/p>\n
# lb8\r\nimport tkinter as tk\r\nfrom random import randint\r\n\r\nroot = tk.Tk()\r\nroot.title(\"Listboxes in Sync\")\r\nroot.geometry(\"400x300+400+200\")\r\n\r\ndef def_listbox(): # => Listbox\r\n\tlb = tk.Listbox(frame1)\r\n\tlb.pack(side=\"left\", expand=1, fill=tk.BOTH)\r\n\r\n\tfor n in range(49):\r\n\t\trnd = str(randint(1,100))\r\n\t\tlb.insert(tk.END, rnd)\r\n\treturn lb\r\n\r\nframe1 = tk.Frame(root)\r\nframe1.pack(expand=1, fill=tk.BOTH)\r\nlb1 = def_listbox()\r\nlb2 = def_listbox()\r\n\r\nroot.mainloop()\r\n<\/pre>\n
You will see this:<\/p>\n
\"\"<\/a><\/p>\n
Live conding listbox tkinter<\/h2>\n