tkinter focus_set() not setting focus

Question

I am trying to set focus on an entry window however I get an error throw every time.

AttributeError: 'NoneType' object has no attribute 'focus_set'

I looked up some examples of this and none of the suggestions worked. I'm assuming I have an error from naming something in my code if the function is just flat out not working.

Here is my code...

import tkinter as tk
from tkinter import ttk


def greet():
    print(f"Hello, {user_name.get() or 'World'}!")


root = tk.Tk()

user_name = tk.StringVar()

name_label = ttk.Label(root, text="Name: ").pack(side="left", padx=(0, 10))
name_entry = ttk.Entry(root, width=15, textvariable=user_name).pack(side="left")

name_entry.focus_set()

greet_button = ttk.Button(root, text="greet", command=greet).pack(side="left")

quit_button = ttk.Button(root, text="quit", command=root.destroy).pack(side="right")

root.mainloop()

I am normally develop we applications in JavaScript so python is a little unfamiliar to me, I am just trying to learn something new. Thanks!

Answer 1

I found the answer but I don't know why it works. If i put pack on another line it works...

name_label = ttk.Label(root, text="Name: ").pack(side="left", padx=(0, 10))
name_entry = ttk.Entry(root, width=15, textvariable=user_name)
name_entry.pack(side="left")
name_entry.focus()