Tkinter - Columns of equal weight are NOT equal width
It is not a bug. weight determines how extra space is allocated. It doesn't make any guarantees about the size of a row or column.
If you want columns to have a uniform width, use the uniform option and make them all be part of the same uniform group.
window.columnconfigure(0,weight=1, uniform='third')window.columnconfigure(1,weight=1, uniform='third')window.columnconfigure(2,weight=1, uniform='third')Note: there is nothing special about 'third' -- it can be any string as long as it's the same string for all three columns.