Trying to grasp the point of putting frames and widgets in classes for tkinter

问题

As the question states, I can't seem to fully grasp the point of using classes with tkinter.

I have read through a decent number of different sites but I keep getting search results on how to create and use classes, but none so far have been able to get through to me. I've even scoured through the suggested questions while asking this one. The closest I've come to understanding is Bryan's explanation on this answer to the question Why use classes when programming a tkinter gui?

But still, I feel like I'm almost there, just not quite over the edge of understanding.

In his example in the link, he creates an unconventional program, and then a better, more conventional program that does the same thing. I know that it represents a much smaller scale than the thousand-line programs that could really benefit from an object oriented approach.

Does every widget need to be in its own separate frame that's maybe part of an even bigger frame?

Can classes have methods that create and place a frame? In addition, can those same classes have methods than can create, modify, and place a widget within the previously made frame?

I also have some code that allows me to create, modify, and place a widget. Although I know it's not conventional, so I would greatly appreciate some input on this as well. Any suggestions on what you would do with this code to make it better?

import tkinter as tk

def layout(self, row=0, column=0, columnspan=None, row_weight=None, column_weight=None, color=None, sticky=None, ipadx=None, padx=None, ipady=None, pady=None):
    self.grid(row=row, column=column, columnspan=columnspan, sticky=sticky, ipadx=ipadx, padx=padx, ipady=ipady, pady=pady)
    self.grid_rowconfigure(row, weight=row_weight)
    self.grid_columnconfigure(column, weight=column_weight)
    self.config(bg=color)

class MyLabels(tk.Label):
    def __init__(self, parent, text, **kwargs):
        tk.Label.__init__(self, parent, text=text)
        layout(self, **kwargs)

class MyButtons(tk.Button):
    def __init__(self, parent, text, command, **kwargs):
        tk.Button.__init__(self, parent, text=text, command=command)
        layout(self, **kwargs)


window = tk.Tk()
test_button = MyButtons(window, "hi", None, color="pink")
window.mainloop()

---

Edited after comments: So I've been working many hours since yesterday trying to incorporate the ideas you've had for me. This is what I came up with:

import tkinter as tk

window = tk.Tk()

class MyWidgets(tk.Frame):
    def __init__(self, parent):
        tk.Frame.__init__(self, parent)
        self.layout()

    def layout(self):
        self.grid(row=0, column=0)
        self.config(bg="blue")

class MyButtons(MyWidgets):
    def __init__(self, parent, text):
        MyWidgets.__init__(self, parent)
        tk.Button(parent, text=text)
        self.layout()

frme = MyWidgets(window)
btn = MyButtons(frme, text="Test")
window.mainloop()

I've tried moving things around and rewriting lots of areas on this little side program, and even though I was able to prove that btn is infact accessing the self.config(bg="blue") attribute, the button doesn't appear to change. As a matter of fact I can't find a way to make the button appear without needing to put self.grid() in the child class just after the button is created.

Still, even if I did add the self.grid() the button still won't turn blue. Is it something with self?

Why won't the button appear when the child class creates it, and the parent class places it?

Note: I've purposefully omitted the entire layout function and replaced it with just a simple config method. I figure if I can understand this, I can then find a way to incorporate the whole function back into the code.

回答1:

Does every widget need to be in its own separate frame that's maybe part of an even bigger frame?

That's a bit like asking if every part of a mathematical expression needs parenthesis. Strictly speaking, the answer is "no". However, using frames to organize groups of widgets is a tool designed to make writing and understanding the code easier, much like parenthesis in a complex math equation makes writing and understanding the equation easier.

Can classes have methods that create and place a frame? In addition, can those same classes have methods than can create, modify, and place a widget within the previously made frame?

Yes, and yes. Methods in a class don't have any limitations on what they can and cannot do. Methods of a class can do anything that a normal function can do.

I also have some code that allows me to create, modify, and place a widget. Although I know it's not conventional, so I would greatly appreciate some input on this as well. Any suggestions on what you would do with this code to make it better?

"Better" is highly subjective. What is better for 20 lines of code might not be better for 200, 2,000, or 20,000. What is better for a function used exactly twice might not be better for a function used hundreds or thousands of times (or visa versa).

That being said, you're doing one thing that is very unconventional and which leads to making your code harder to understand: you're using self as a parameter for a function that is not a method of a class. self means something very specific to python programmers; using it outside of the context of a method is very confusing.

You should do one of two things for the method layout:

• Rename self to be widget or any other term other than self
• Create a base class that defines layout, and then have your classes inherit from the base class. In that case, self is the proper first argument.

---

This part of the answer refers to code which was added after I wrote my original answer.

The base class I was referring to needs to be a separate class. For example:

class Base():
    def layout(self):
        self.grid(row=0, column=0)
        self.config(bg="blue")

class MyLabels(Base, tk.Label):
    def __init__(self, parent, text, **kwargs):
        tk.Label.__init__(self, parent, text=text)
        self.layout(self, **kwargs)

class MyButtons(Base, tk.Button):
    def __init__(self, parent, text, command, **kwargs):
        tk.Button.__init__(self, parent, text=text, command=command)
        self.layout(self, **kwargs)

This type of class is sometimes called a mixin because it's not designed to be instantiated as a standalone object. Rather, it "mixes in" some additional behavior to other classes. A mixin will typically have methods, but won't have its own __init__.

来源：https://stackoverflow.com/questions/60676512/trying-to-grasp-the-point-of-putting-frames-and-widgets-in-classes-for-tkinter