Where to put event handlers and pass variables to it?

Question

I've been trying to bind a mouseclick to a grid in a certain frame, after this question I made a new class and bound the event to that, which works. But the function of the mouse event needs a variable that is made in the MainApp class, I can't get it to work properly. Depending on the arrangement either I can't get the widgets variable to be used in the function, or the order of functions/classes is wrong and thus the program won't find something because it is referenced too soon.

So my main question is how do I get the function working, which I think mostly involves where do I put that thing? As a function in the Schedule_Label class? as a function of the MainApp ? A loose function? Is it smarter to put all the event handlers in a seperate Python file and import that?

Excluding some code this is what is happening:

class Schedule_Label(tk.Label):
    def __init__(self, parent, *args, **kwargs):
        tk.Label.__init__(self, parent, *args, **kwargs)
        self.bind("<Button-1>", mouse_1)

...
class Schedule, this class uses Schedule_Label

class MainApp(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        tk.Frame.__init__(self, parent, *args, **kwargs)
        #class schedule is used here
        ...
        schedule_widgets = self.schedule.New(date, stafflist)
        ...

def mouse_1(event):
    r = event.widget.grid_info()['row']
    c = event.widget.grid_info()['column']
    schedule_widgets[(r,c)].configure(state="active")

if __name__ == "__main__":
    root = tk.Tk()
    app = MainApp(root)
    app.pack()
    root.mainloop()

Answer 1

You are calling schedule_widgets from mouse_1 , which is in the name space of MainApp , to be able to use it like that use global keyword.

schedule_widgets = None#--------------------------------------------------------  new ---

class Schedule_Label(tk.Label):
    def __init__(self, parent, *args, **kwargs):
        tk.Label.__init__(self, parent, *args, **kwargs)
        self.bind("<Button-1>", mouse_1)

...
class Schedule, this class uses Schedule_Label

class MainApp(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        global schedule_widgets #-----------------------------------------------  new ---
        tk.Frame.__init__(self, parent, *args, **kwargs)
        #class schedule is used here
        ...
        schedule_widgets = self.schedule.New(date, stafflist)
        ...

def mouse_1(event):
    global schedule_widgets #---------------------------------------------------  new ---
    r = event.widget.grid_info()['row']
    c = event.widget.grid_info()['column']
    schedule_widgets[(r,c)].configure(state="active")

if __name__ == "__main__":
    root = tk.Tk()
    app = MainApp(root)
app.pack()
root.mainloop()

There is an other way to do it, but schedule_widgets should be an attributes of MainApp and when you instantiate schedule_Label you should give parent reference so that mouse_1 can access schedule_widgets with parent reference

class Schedule_Label(tk.Label):
    def __init__(self, parent, *args, **kwargs):
        tk.Label.__init__(self, parent, *args, **kwargs)
        self.bind("<Button-1>", lambda event, p=parent: mouse_1(event, p)) # ---  new ---

...
class Schedule, this class uses Schedule_Label

class MainApp(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        tk.Frame.__init__(self, parent, *args, **kwargs)

        #class schedule is used here
        ...
        self.schedule_widgets = self.schedule.New(date, stafflist) #------------  new ---
        ...

def mouse_1(event, parent): #---------------------------------------------------  new ---
    r = event.widget.grid_info()['row']
    c = event.widget.grid_info()['column']
    parent.schedule_widgets[(r,c)].configure(state="active") #------------------  new ---
if __name__ == "__main__":
    root = tk.Tk()
    app = MainApp(root)
    app.pack()
    root.mainloop()