Tkinter bind only works once

Question

I cannot find any reason that this bind isn't working. I have tried setting focus, moving the bind outside of the class, among other things. The strange thing is it works once at the beginning of the program. This leads me to believe that the bind does work but not as intended.

import tkinter as tk
import os
import Themes

##########################################################################
root = tk.Tk()

topleft = tk.Frame(root,
               bg = 'red',
               )

topmid = tk.Frame(root,
              bg = 'white',
              )

topright = tk.Frame(root,
                bg = 'blue',
                )

bottomleft = tk.Frame(root,
                  bg = 'yellow',
                  )

bottommid = tk.Frame(root,
                  bg = 'green',
                  )

bottomright = tk.Frame(root,
                    bg = 'black',
                    )

tk.Grid.rowconfigure(root, 0, weight = 20)
tk.Grid.columnconfigure(root, 0, weight = 30)
topleft.grid(row = 0, column = 0,
         sticky = tk.N+tk.E+tk.S+tk.W,
         rowspan = 2, columnspan = 1)

tk.Grid.columnconfigure(root, 1, weight = 20)
topmid.grid(row = 0, column = 1,
        sticky = tk.N+tk.E+tk.S+tk.W,
        rowspan = 1, columnspan = 2)

tk.Grid.columnconfigure(root, 3, weight = 85)
topright.grid(row = 0, column = 3,
          sticky = tk.N+tk.E+tk.S+tk.W,
          rowspan = 3, columnspan = 1)

tk.Grid.rowconfigure(root, 2, weight = 40)
bottomleft.grid_propagate(False)
bottomleft.grid(row = 2, column = 0,
            sticky = tk.N+tk.E+tk.S+tk.W,
            rowspan = 1, columnspan = 3)

tk.Grid.rowconfigure(root, 1, weight = 10)
tk.Grid.columnconfigure(root, 1, weight = 10)
bottommid.grid(row = 1, column = 1,
           sticky = tk.N+tk.E+tk.S+tk.W,
           rowspan = 1, columnspan = 1)

tk.Grid.rowconfigure(root, 1, weight = 10)
tk.Grid.columnconfigure(root, 2, weight = 10)
bottomright.grid(row = 1, column = 2,
             sticky = tk.N+tk.E+tk.S+tk.W,
             rowspan = 1, columnspan = 1)
##########################################################################

class File_selector:
    def __init__(self):
    self.scrollbar = tk.Scrollbar(bottomleft,
                                  orient = 'vertical'
                                  )
    self.listbox = tk.Listbox(bottomleft,
                              yscrollcommand = self.scrollbar.set
                              )
    self.check = print(self.listbox.curselection())

    self.scrollbar['command'] = self.listbox.yview

    for file in os.listdir(os.curdir):
        if file.endswith(".py"):
            self.listbox.insert(tk.END, file)

    self.listbox.bind('<<ListboxSelect>>', lambda e: self.check)

    self.grid()
    def grid(self):      
    self.scrollbar.grid(row = 0, column = 1, sticky = tk.N+tk.S)

    tk.Grid.rowconfigure(bottomleft, 0, weight = 1)
    tk.Grid.columnconfigure(bottomleft, 0, weight = 1)
    self.listbox.grid(row = 0, column = 0,
                      sticky = tk.N+tk.E+tk.S+tk.W)

File_selector()
root.mainloop()

that triggers once on any select ... you then need to get the selected item ... — Joran Beasley, Dec 21 '15 at 03:39
Doesn't `self.check` do that? For the moment i'm just trying to get the program to acknowledge me clicking the listbox. @Joran — Tyron Marshall, Dec 21 '15 at 03:42

furas · Accepted Answer · 2015-12-21T04:31:45.783

1

Line

self.check = print(self.listbox.curselection())

is incorrect.

It runs print() and prints text on screen (when File_selector object is created) and then it assigns None to self.check (because print() returns None)

You need normal function

def check(self, event):
    print(self.listbox.curselection())

or lambda function

self.check = lambda event:print(self.listbox.curselection())

And then you can bind

self.listbox.bind('<<ListboxSelect>>', self.check)

edited Dec 21 '15 at 04:31

answered Dec 21 '15 at 04:15

furas

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This works perfectly. Thanks a lot! For future is there anyway for me to check if anything is returning `None`? – Tyron Marshall Dec 21 '15 at 13:20
Python functions return None by default. Read the doc or the docstring or use `help(func)` to find out about non-default returns. – Terry Jan Reedy Dec 21 '15 at 23:08

Tkinter bind only works once

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