Python 3 classes error

Question

I'm trying to make a little program by using classes. So far, I've made two classes, in which the first one will run the next one. When I run this, I get an error message. I don't understand what's wrong, but it looks like it has something do to about that I define the name Menu1 before it's been read. I'm going to create a new function after these classes, that'll first run MainWindow, and then Menu1. I would appreciate help.

Code:

class MainWindow:
    app = Tk()
    app.title("MyApp")
    window = Frame(app, width=1050, height=550)
    app.minsize(width=1050, height=550)
    window.pack()
    menu = Menu1()
    menu.makeMenu()
    app.mainloop()


class Menu1:
    def makeMenu(self):
        app.config(menu=menu)
        menu.add_cascade(label="Settings", menu=subMenu)
        subMenu.add_command(label="Settings", command=settings1)

def settings1():
    print("Open new window")


if __name__ == "__main__":
    MainWindow()

Error message:

Traceback (most recent call last):
  File "", line 7, in <module>
    class MainWindow:
  File "", line 13, in MainWindow
    menu = Menu1()
NameError: name 'Menu1' is not defined

Process finished with exit code 1

Proud anti-zionist · Accepted Answer · 2018-08-09 08:50:05Z

5

Everything under class MainWindow is run immediately. It is not in a method. At that point class Menu1 has not yet been executed and no class by that name exists yet.

It looks like you really only wanted MainWindow to be a function instead:

def main_window():
    app = Tk()
    app.title("MyApp")
    window = Frame(app, width=1050, height=550)
    app.minsize(width=1050, height=550)
    window.pack()
    menu = Menu1()
    menu.makeMenu()
    app.mainloop()

(I used a lowercase letter this time, as the Python style guide reserves camel-case names for classes).

Your next problem is that Menu1.makeMenu() has no access to the app local variable in main_window(); you would need to pass that in:

menu = Menu1()
menu.makeMenu(app)

and

class Menu1:
    def makeMenu(self, app):
        app.config(menu=self)
        menu.add_cascade(label="Settings", menu=subMenu)
        subMenu.add_command(label="Settings", command=setting1)

Note that I changed menu to self there, menu was another local name in main_window.

The code still won't work because you haven't defined the name subMenu anywhere, but this is at least a step or 2 closer.

edited Aug 9, 2018 at 8:50

Proud anti-zionist

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answered Jan 9, 2017 at 15:47

Martijn Pieters

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3 Comments

Proud anti-zionist Over a year ago

Thank you very much. I'll go back look a little more at my earlier testing files as well.

Proud anti-zionist Over a year ago

Is there anyway to make this work without removing the first class?

Martijn Pieters Over a year ago

@Andreas: Sure, take a look at effbot.org/tkinterbook/tkinter-hello-again.htm on how to use classes properly. You are not really using classes correctly here.

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