It's simple: just do not do what most beginners seems to try, which is to have the dialog know anything about or be able to call anything in the MainWindow! That is the wrong way to go. Other windows/dialogs/classes should know nothing about your main window, do not even allow yourself to import the MainWindow module inot any other module so you won't be tempted.

Assuming you mean only MainWindow knows the list of names to populate the combobox, write yourself a utility "setter" method in the dialog to receive the list to be used and it populates the combobox. And maybe a "getter" method to return which one selected if wanted by the outside world. Something like:

# MainWindow
import MyDialog

myDialog = MyDialog(self)
myDialog.setComboItems(["abc", "def", ...])
if myDialog.exec():
    chosenItem = myDialog.comboItem()

# MyDialog
def setComboItems(self, items):
    self.combo.addItems(items)

def comboItem(self):
    return self.combo.currentText()

Hahaha that's a really good example. Yeah, I'd definitely prefer to ask them for the information.

Thank you so much! :)

For the rest as @mpergand said.

I would suggest you would find your life easier if you try not to call into parent from children. Qt can also make this easier with its signals/slots mechanism.

That would be an example of what I shouldn't do, right?

Nothing is 100% bad or good.
You need to understand what you are doing.
When you pass a reference of your MainWidow to the Dialog, you create a strong dependency between the two objects (tight coupling)
Work well in your case, now suppose you need the same utility dialog somewhere else in your program where you have no access to the Maindow , you're doomed :)

By experience, programmers know that creating tight coupling is bad and can lead to nightmare issues.
And the main avantage of object programming is to produce reusable objects, so you must have this in mind and eliminate all dependencies as much as possible.

I want to be 1000% clear. I've seen a lot of examples of people accessing parent attributes whitin QDialog saving a parent reference or accessing them as self.parent().attribute_name.

That would be an example of what I shouldn't do, right?

Thanks again.

Nice, I got it! Happy Holidays!

It's simple: just do not do what most beginners seems to try, which is to have the dialog know anything about or be able to call anything in the MainWindow! That is the wrong way to go. Other windows/dialogs/classes should know nothing about your main window, do not even allow yourself to import the MainWindow module inot any other module so you won't be tempted.

Assuming you mean only MainWindow knows the list of names to populate the combobox, write yourself a utility "setter" method in the dialog to receive the list to be used and it populates the combobox. And maybe a "getter" method to return which one selected if wanted by the outside world. Something like:

# MainWindow
import MyDialog

myDialog = MyDialog(self)
myDialog.setComboItems(["abc", "def", ...])
if myDialog.exec():
    chosenItem = myDialog.comboItem()

# MyDialog
def setComboItems(self, items):
    self.combo.addItems(items)

def comboItem(self):
    return self.combo.currentText()