Basic formatting

Simple positional formatting is probably the most common use-case. Use it if the order of your arguments is not likely to change and you only have very few elements you want to concatenate.
Since the elements are not represented by something as descriptive as a name this simple style should only be used to format a relatively small number of elements.

Old

'%s %s' % ('one', 'two')

New

'{} {}'.format('one', 'two')

Output

one two

Old

'%d %d' % (1, 2)

New

'{} {}'.format(1, 2)

Output

1 2