How can I choose coordinate of tkinter frame?

Widgets will by default be centered in their allocated space within the container.

Your code at the moment doesn't work, so I've changed it to this (I think it mimics what you're saying you currently have):

import tkinter as tkroot = tk.Tk()root.geometry("600x400")redFrame = tk.Frame(root, bg='red')redFrame.pack_propagate(0)redFrame.pack(fill='both', side='left', expand='True')blueFrame = tk.Frame(root, bg='blue')blueFrame.pack_propagate(0)blueFrame.pack(fill='both', side='right', expand='True')greenFrame = tk.Frame(redFrame, width=100, height=100, bg='green')greenFrame.pack_propagate(0)greenFrame.pack(side='top', padx=0, pady=0)root.mainloop()

If you run this code, the greenFrame will appear as your image shows, at the top and centered inside redFrame.

If you want greenFrame to appear at the top left of redFrame, you can change the anchor point of the frame:

greenFrame = tk.Frame(redFrame, width=100, height=100, bg='green')greenFrame.pack_propagate(0)greenFrame.pack(side='top', padx=0, pady=0, anchor='w')

That is because when you do side="top" using pack, the widget gets allocated an entire strip of horizontal space. It gets centered within that space by default:

If you do side="left", then the widget gets allocated an entire strip of vertical space, and it gets centered in that space by default.

However in both cases you can change the anchor point, so that your component is placed differently within that allocated spaces.

This is the code which achieves what (I think) you want:

import tkinter as tkroot = tk.Tk()root.geometry("600x400")redFrame = tk.Frame(root, bg='red')redFrame.pack_propagate(0)redFrame.pack(fill='both', side='left', expand='True')blueFrame = tk.Frame(root, bg='blue')blueFrame.pack_propagate(0)blueFrame.pack(fill='both', side='right', expand='True')greenFrame = tk.Frame(redFrame, width=100, height=100, bg='green')greenFrame.pack_propagate(0)greenFrame.pack(side='top', padx=0, pady=0, anchor='w')root.mainloop()