from math import pi
print '%10f' % pi # Field width 10
print '%10.2f' % pi # Field width 10, precision 2
print '%.2f' % pi # Precision 2
print '%.5s' % 'Guido van Rossum'
use an * as the width or precision (or both), in which case the number will be read from the tuple argument
print '%.*s' % (5, 'Guido van Rossum')