For pleasant and effective rendering of diagrams, sometimes it is a good idea to pay attention to cap and join styles.
The cap style of a line is the shape of the end of the line. Styles are:
tk.BUTT: The end of the line is cut
off square at a line that passes through the
tk.PROJECTING: The end of the line is
cut off square, but the cut line projects past
the endpoint a distance equal to half the line's
tk.ROUND: The end describes a
semicircle centered on the endpoint.
The join style describes the shape where two line segments meet at an angle.
tk.ROUND: The join is a circle
centered on the point where the adjacent
line segments meet.
tk.BEVEL: A flat facet is drawn
at an angle intermediate between the angles
of the adjacent lines.
tk.MITER: The edges of the adjacent
line segments are continued to meet at a sharp
This illustration shows how Tkinter's cap and join options work with a line made of two connected line segments. Small red circles show the location of the points that define this line.