How do I add a separator line in tkinter?
Use ttk.Separator with an orient, and give it a length when you place it. On its own a separator has no size, which is why the usual first attempt appears to do nothing at all.
import tkinter as tk
from tkinter import ttk
root = tk.Tk()
tk.Label(root, text="Account").pack()
ttk.Separator(root, orient="horizontal").pack(fill="x", pady=8)
tk.Label(root, text="Payment").pack()
root.mainloop()Why yours is invisible
A separator asks for no space of its own: packed without fill, a horizontal one measures one pixel by one pixel, which is a dot you will never find on a 300-pixel window. Adding fill="x" stretches it across its parent and it appears immediately, at one pixel tall and as wide as the space allows.
The same applies to a vertical separator, which needs fill="y" to have any height. In a grid, sticky="ew" and sticky="ns" do the same job, and a horizontal rule usually wants columnspan so it crosses the whole layout rather than one column.
ttk.Separator(root, orient="horizontal").pack(fill="x")
ttk.Separator(root, orient="vertical").pack(side="left", fill="y")
# in a grid
ttk.Separator(root, orient="horizontal").grid(row=2, columnspan=3, sticky="ew")Giving it breathing room
A divider works by the space around it as much as the line itself, so pad it rather than butting it against the widgets on either side. pady on a horizontal separator and padx on a vertical one is usually enough to make a window read as sections rather than a list.
When a separator is the wrong answer
If the widgets either side belong together and the line is there to say so, a LabelFrame states the grouping outright and gives it a caption. Reach for a separator when you want a break with no name attached to it.
Doing it without the lookup
Drag a Separator on and give it a width on the canvas — because the designer places widgets absolutely, it already has a length, so the invisible-separator problem cannot happen. The orientation is a dropdown in the inspector.
Lay the window out visually and read the generated Python as you go.
Open the tkinter designer →