Setting the position on a button in Python?

Causing a widget to appear requires that you position it using with what Tkinter calls "geometry managers". The three managers are grid, pack and place. Each has strengths and weaknesses. These three managers are implemented as methods on all widgets.

grid, as its name implies, is perfect for laying widgets in a grid. You can specify rows and columns, row and column spans, padding, etc.

Example:

b = Button(...)
b.grid(row=2, column=3, columnspan=2)

pack uses a box metaphor, letting you "pack" widgets along one of the sides of a container. pack is extremely good at all-vertical or all-horizontal layouts. Toolbars, for example, where widgets are aligned in a horizontal line, are a good place to use pack.

Example:

b = Button(...)
b.pack(side="top", fill='both', expand=True, padx=4, pady=4)`

place is the least used geometry manager. With place you specify the exact x/y location and exact width/height for a widget. It has some nice features such as being able to use either absolute or relative coordinates (for example: you can place a widget at 10,10, or at 50% of the widgets width or height).

Unlike grid and pack, using place does not cause the parent widget to expand or collapse to fit all of the widgets that have been placed inside.

Example:

b = Button(...)
b.place(relx=.5, rely=.5, anchor="c")

With those three geometry managers you can do just about any type of layout you can imagine.

Try Grid Geometry Manager:

btns = [
    (lambda ctl: ctl.grid(row=r, column=c) or ctl)(
        Button(text=str(1 + r * 3 + c)))
    for c in (0,1,2) for r in (0,1,2)]

result:

[1][2][3]
[4][5][6]
[7][8][9]

astynax is right. To follow the example you gave:

MyButton1 = Button(master, text="BUTTON1", width=10, command=callback)
MyButton1.grid(row=0, column=0)

MyButton2 = Button(master, text="BUTTON2", width=10, command=callback)
MyButton2.grid(row=1, column=0)

MyButton3 = Button(master, text="BUTTON3", width=10, command=callback)
MyButton3.grid(row=2, column=0)

Should create 3 row of buttons. Using grid is a lot better than using pack. However, if you use grid on one button and pack on another it will not work and you will get an error.