Python tkinter禁用"submit“按钮，直到填充完所有字段

import tkinter as tk

def check_fields():
    if len(name_entry.get()) > 0 and len(email_entry.get()) > 0:
        submit_btn.config(state=tk.NORMAL)
    else:
        submit_btn.config(state=tk.DISABLED)

root = tk.Tk()

name_label = tk.Label(root, text="Name:")
name_label.pack()
name_entry = tk.Entry(root)
name_entry.pack()

email_label = tk.Label(root, text="Email:")
email_label.pack()
email_entry = tk.Entry(root)
email_entry.pack()

submit_btn = tk.Button(root, text="Submit", state=tk.DISABLED)
submit_btn.pack()

name_entry.bind("<KeyRelease>", lambda event: check_fields())
email_entry.bind("<KeyRelease>", lambda event: check_fields())

root.mainloop()