There are a number of ways of getting callbacks when Text or Entry widgets are changed in Tkinter, but I haven't found one for Listbox's (it doesn't help that much of the event documentation I can find is old or incomplete). Is there some way of generating an event for this?
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4All virtual events are listed at: The Tcl/Tk man pages.Bill– Bill2013-03-04 02:32:38 +00:00Commented Mar 4, 2013 at 2:32
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3 Answers
def onselect(evt):
# Note here that Tkinter passes an event object to onselect()
w = evt.widget
index = int(w.curselection()[0])
value = w.get(index)
print('You selected item %d: "%s"' % (index, value))
lb = Listbox(frame, name='lb')
lb.bind('<<ListboxSelect>>', onselect)
answered Oct 17, 2012 at 13:57
Pierre-Jean Coudert
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2 Comments
drevicko
Minor point, but this only prints the first of the selected entries. If you've multiple selections, try something like
print 'You selected items: %s'%[w.get(int(i)) for i in w.curselection()]
ismailarilik
In Python 3.6.5,
int(w.curselection()[0]) can be replaced with w.curselection()[0] because it already returns an object of type int. Notice that I didn't try this with any other Python version.You can bind to the <<ListboxSelect>> event. This event will be generated whenever the selection changes, whether it changes from a button click, via the keyboard, or any other method.
Here's a simple example which updates a label whenever you select something from the listbox:
import tkinter as tk
root = tk.Tk()
label = tk.Label(root)
listbox = tk.Listbox(root)
label.pack(side="bottom", fill="x")
listbox.pack(side="top", fill="both", expand=True)
listbox.insert("end", "one", "two", "three", "four", "five")
def callback(event):
selection = event.widget.curselection()
if selection:
index = selection[0]
data = event.widget.get(index)
label.configure(text=data)
else:
label.configure(text="")
listbox.bind("<<ListboxSelect>>", callback)
root.mainloop()
This event is mentioned in the canonical man page for listbox. All predefined virtual events can be found on the bind man page.
1 Comment
drevicko
@RobotGymnast Try (The Tcl/Tk man pages)[tcl.tk/man/tcl8.5/TkCmd/event.htm#M41] (from Bill's answer below)
I had the problem that I needed to get the last selected item in a listbox with selectmode=MULTIPLE. In case someone else has the same problem, here is what I did:
lastselectionList = []
def onselect(evt):
# Note here that Tkinter passes an event object to onselect()
global lastselectionList
w = evt.widget
if lastselectionList: #if not empty
#compare last selectionlist with new list and extract the difference
changedSelection = set(lastselectionList).symmetric_difference(set(w.curselection()))
lastselectionList = w.curselection()
else:
#if empty, assign current selection
lastselectionList = w.curselection()
changedSelection = w.curselection()
#changedSelection should always be a set with only one entry, therefore we can convert it to a lst and extract first entry
index = int(list(changedSelection)[0])
value = w.get(index)
tkinter.messagebox.showinfo("You selected ", value)
listbox = tk.Listbox(frame,selectmode=tk.MULTIPLE)
listbox.bind('<<ListboxSelect>>', onselect)
listbox.pack()
