app structuring / re importing modules with tkinter python3 - python-3.x

Question

I am restructuring this question: I felt the original questions were long winded and not particularly helpful to anyone else.
I have a main app (run as__main__) that runs directly.
I have a module (simple_module.py) that I only wish to use as an import.
I realise that I can run it standalone if required (via if__name__) and have including that in the modules code, for demonstration only.
When user presses main.py's 'start' button, it should open a new toplevel window with all the classes and widgets from the simple_module which are all in a single class called Page. (all whilst the main app window remains open.)
I want the module to be re-imported (or equivalent) every time the button is pressed. When the modules 'close' button or X is pressed I want it to close that window. main.py's window remains open throughout this and the button press needs to re-open that module window, infinitely, like a loop.
I have added if name == 'main' just to highlight that I understand what this does (it is normally within all my main.py apps) and why I still cannot get the result I want. As far as I can see, it does not change anything, I am now only importing the class but 'new' is still not recognised. Which is the same issue as in the prior example.
I have main.py
import tkinter as tk
# audio module works as expected
import audio_module as am
# I want this window to open and close on command
import simple_module as sm
class GUI(tk.Frame):
def __init__(self, *args, **kwargs):
tk.Frame.__init__(self, *args, **kwargs)
#self.new = tk.Toplevel(self) # auto loads a second, unwanted window
self.session_counter = 0
self.start_btn = tk.Button(root, text="start", command=self.start)
self.start_btn.grid(row=4,column=0,sticky="nsew",pady=30, padx=30, ipady=18)
def start(self):
am.spell() # these audio imports work like a charm, every btn press - single functions call OK
self.session_counter += 1
print(self.session_counter)
#import simple_module - if used here, my usual 'illegal' import style (works great, once only,
# unless in same script as __main__ in which case all re-imports work fine)
# Import attempts
#import simple_module as sm
#page = Page(new) # Page not defined
#sm.Page() #missing parent arg (new)
# error: 'new' not defined
#sm.Page(new)
if __name__ == '__main__':
print('running as __main__')
root = tk.Tk()
#sm.Page = tk.Toplevel(new) # a desperate attempt NO
#page = sm.Page(tk.TopLevel) NO
# qualify and USE module here! sm is not required if you use 'from simple_module import Page' !!
page = sm.Page(root)
#page.pack(fill='both', expand=True)
page.grid(row=0,column=0,sticky='nsew')
main = GUI(root)
root.mainloop()
Finally, we have simple_module.py:
import tkinter as tk
import audio_module as am
# this module works exactly as expected IF run directly...
class Page(tk.Frame):
def __init__(self, parent, *args, **kwargs):
tk.Frame.__init__(self, parent, *args, **kwargs)
# super().__init__(*args, **kwargs)
self.back_btn = tk.Button(parent, text="close", command=self.back)
self.back_btn.grid(row=4,column=0,sticky="nsew",pady=30, padx=30, ipady=18)
def back(self):
am.click()
# close this page BUT have it ready to re-open IF user re-presses button.
new.destroy()
if __name__ == "__main__":
print('running as __main__ directly')
new = tk.Tk()
#new = tk.Toplevel() # this loads an unwanted additional blank window. IF run directly.
page = Page(new)
# the missing line to self contain module!
#page.pack(fill='both', expand=True)
page.grid(row=0,column=0,sticky='nsew')
new.mainloop()
else:
print('running as import with __name__ ==',__name__)
Thanks for your patience and responses. I have re-studied the if main guide you provided a link to, it re-affirms what I already believe I knew about it. A useful example in there for when I want to open a single frame only and switch between them, but in this case I want the main window to remain open whilst calling the modules window.

Answer 1

The problem you're facing is that your Page class isn't written to be reusable. It's relying on global variables and knowledge about the code that is calling it. To be reusable, the Page class needs to be self-contained.
In short, that means that every widget created by Page must be inside the Page class and not in the root window. Also, the code that creates an instance of Page needs to be responsible for calling pack, place, or grid on the instance.
So, the first step is to modify Page so that it can be reusable. The key to that is to require that the caller pass in the parent widget. You're doing that, but you aren't using the passed-in value.
Page should look like the following code. Notice that it explicitly declares parent as the first positional argument, and it passes that on to tk.Frame.__init__:
class Page(tk.Frame):
def __init__(self, parent, *args, **kwargs):
tk.Frame.__init__(self, parent, *args, **kwargs)
self.back_btn = tk.Button(parent, text="close", command=self.back)
...
Notice how the back button is a child of parent rather than the child of some global variable. This is the important step that you are missing, and this is what allows Page to be self-contained and not tightly coupled to the code that creates it.
Once Page is properly self-contained, it is the responsibility of the code that creates an instance of Page to call pack, place, or grid on the instance.
For example, simple_module.py might have this block at the end:
if __name__ == "__main__":
new = tk.Tk()
page = Page(new)
page.pack(fill="both", expand=True)
new.mainloop()
In main.py, since you are importing simple_module as a whole, you need to fully qualify the use of Page:
import simple_module as sm
...
root = tk.Tk()
page = sm.Page(root)
page.pack(fill="both", expand=True)
root.mainloop()
Alternately, you could just import Page and omit the sm.:
from simple_module import Page
...
page = Page(root)
...
Notice how one file can use root and one can use new, but your code will work in either case because it doesn't rely on a global variable. Inside of page it will always be parent no matter what the caller called it.
As an aside, you don't have to import simple_module inside start -- you only need to import it once at the start of the program.