Chris Roy-Smith wrote:
> OS: Linux Chris-X451MA 4.4.0-97-generic #120-Ubuntu SMP Tue Sep 19
> 17:28:18 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
>
> Python 3.5.2 (default, Sep 14 2017, 22:51:06)
>
> I am trying to learn how to use a tkinter listbox. When I execute my
> experimental code, an odd index is printed immediately (output below
> code), index looks wrong (shouldn’t it be an integer). Also it doesn't
> print new values when I select an entry.
>
> ---------------------------------------------------
>
> #!/usr/bin/python3
> #test listbox
> from tkinter import *
>
> class Dialog(Frame):
>
> def __init__(self, master):
> Frame.__init__(self, master)
> self.list = Listbox(self, selectmode=EXTENDED)
> self.list.pack(fill=BOTH, expand=1)
> self.current = None
> self.poll() # start polling the list
>
> def poll(self):
> now = self.list.curselection()
> if now != self.current:
> self.list_has_changed(now)
> self.current = now
> self.after(250, self.poll)
>
> def list_has_changed(self, selection):
> print ("selection is", selection)
>
>
> snames=('fred', 'george', 'manuel', 'john', 'eric', 'terry')
> master = Tk()
>
> listbox = Listbox(master)
> listbox.grid(row=0)
>
> for item in snames:
> listbox.insert(END, item)
The problem is your inconsistent use of the Dialog class which you do not
instantiate.
> myindicator=Dialog.list_has_changed(master, listbox)
Here you call list_has_changed() like a function. The first argument (self)
is your `master` object, the second is the listbox. In a nutshell you are
doing
>>> from tkinter import *
>>> master = Tk()
>>> listbox = Listbox(master)
>>> print(listbox)
.140206885684560
and what is displayed when you are printing a tkinter widget is its Tcl/Tk
name -- which admittedly looks odd.
> mainloop()
A fix with minimal changes might be
#!/usr/bin/python3
#test listbox
from tkinter import *
class Dialog(Frame):
def __init__(self, master):
Frame.__init__(self, master)
self.list = Listbox(self, selectmode=EXTENDED)
self.list.pack(fill=BOTH, expand=1)
self.current = None
self.poll() # start polling the list
def poll(self):
now = self.list.curselection()
if now != self.current:
self.list_has_changed(now)
self.current = now
self.after(250, self.poll)
def list_has_changed(self, selection):
print ("selection is", selection)
snames=('fred', 'george', 'manuel', 'john', 'eric', 'terry')
master = Tk()
dialog = Dialog(master)
dialog.pack()
for item in snames:
dialog.list.insert(END, item)
mainloop()
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