urwid GridFlow

#!/usr/bin/python3
import urwid

palette = [('focus', 'white', 'black'),
           ('unfocused', 'black', 'dark green')]

def do_reply(input):
    if input == 'tab':
        if columns.get_focus() == flow1:
            columns.set_focus(flow2)
        else:
            columns.set_focus(flow1)

buttons = [urwid.AttrMap(urwid.Button(str(x)), 'unfocused', focus_map='focus')
           for x in range(30)]
flow1 = urwid.Filler(urwid.GridFlow(buttons, 10, 10, 10, 'center'))
flow2 = urwid.Filler(urwid.GridFlow(buttons, 10, 10, 10, 'center'))
columns = urwid.Columns([flow1, flow2])
loop = urwid.MainLoop(columns, unhandled_input=do_reply, palette=palette)
loop.run()