Tkinter long-running window freezes
John O'Hagan
research at johnohagan.com
Tue Mar 2 19:11:29 EST 2021
On Wed, 24 Feb 2021 22:35:32 +1100
John O'Hagan <research at johnohagan.com> wrote:
> Hi list
>
> I have a 3.9 tkinter interface that displays data from an arbitrary
> number of threads, each of which runs for an arbitrary period of time.
> A frame opens in the root window when each thread starts and closes
> when it stops. Widgets in the frame and the root window control the
> thread and how the data is displayed.
>
> This works well for several hours, but over time the root window
> becomes unresponsive and eventually freezes and goes grey. No error
> messages are produced in the terminal.
>
> Here is some minimal, non-threaded code that reproduces the problem on
> my system (Xfce4 on Debian testing):
>
> from tkinter import *
> from random import randint
>
> root = Tk()
>
> def display(label):
> label.destroy()
> label = Label(text=randint(0, 9))
> label.pack()
> root.after(100, display, label)
>
> display(Label())
> mainloop()
>
> This opens a tiny window that displays a random digit on a new label
> every .1 second. (Obviously I could do this by updating the text
> rather than recreating the label, but my real application has to
> destroy widgets and create new ones).
>
> This works for 3-4 hours, but eventually the window freezes.
Thanks to those that replied to this.
To summarise my tentative and incomplete conclusions, it seems that
tkinter doesn't like a lot of widgets being created and destroyed in a
long running process and will/may eventually freeze if this is done,
for a reason I haven't been able to fathom. Tk internally keeps names
of all widgets created, and this will cause a slow memory-use increase
if not prevented by manually re-using widget names, but this is not the
cause of the freezing.
Here is a simplified version of how I worked around the issue by
recycling widgets:
from tkinter import *
class WidgetHandler:
"Reuse tkinter widgets"
widget_cache = []
def __init__(self, main_window, *args):
self.datastream = MyDataStream(*args)
self.main_window = main_window
if self.widget_cache:
self.widget = self.widget_cache.pop()
self.clean(self.widget)
else:
self.widget = self.new_widget()
#add functionality to widgets, e.g:
self.widget.var.traceid = self.widget.var.trace('w', self.meth1)
self.widget.button.configure(command=self.meth2)
self.widget.button.pack()
#etc
self.widget.pack()
def clean(self, widget):
"Remove traces, clear text boxes, reset button states etc"
#e.g:
self.widget.var.trace_remove('write', var.traceid)
self.widget.button['state'] = 'normal'
#etc
def new_widget(self):
"Create widget and children without adding any commands, traces etc"
widget = Frame(self.main_window)
#e.g:
widget.var = StringVar()
widget.button = Checkbutton(widget, variable=widget.var)
#etc
return widget
def meth1(self, *e):
pass
#do something with self.datastream
def meth2(self):
pass
#do something else with self.datastream
#etc
def quit(self):
self.datastream.quit()
self.widget.pack_forget()
self.widget_cache.append(self.widget)
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