import time

# python3.6.1: `%s` is 10 tiems faster than `format`
>>> t1=time.time();c=['%s %s' %(1, 2) for i in range(10000)];time.time()-t1
0.0005083084106445312
>>> t1=time.time();c=['{0} {1}'.format(1, 2) for i in range(10000)];time.time()-t1
0.005129098892211914

# python2.7.10 `%s` is 2 tiems faster than `format`
>>> t1=time.time();c=['{0} {1}'.format(1, 2) for i in range(10000)];time.time()-t1
0.00415802001953125
>>> t1=time.time();c=['%s %s' %(1, 2) for i in range(10000)];time.time()-t1
0.002238035202026367

# Python3 VS Python2: `%s` is faster, and `format` is slower