#! /usr/bin/env python """ (Q): which way to use for concatenating strings? (A): run the script and find out yourself. """ import time bloated_string = 'bloat me' * 10 # method 1, simple concatenation def slow(): test_string = '' start = time.clock() for i in range(1000): test_string += bloated_string end = time.clock() delta = float(end-start) # print 'slow len: ', len(test_string) return delta # method 2, use list.append() and ''.join() def fast(): test_string = list() start = time.clock() for i in range(1000): test_string.append('%s' % bloated_string) test_string = ''.join(test_string) end = time.clock() delta = float(end-start) # print 'fast len: ', len(test_string) return delta # method 3, use list comprehension and ''.join() def fastest(): test_string = bloated_string start = time.clock() test_string = ''.join([test_string for i in range(1000)]) end = time.clock() delta = float(end-start) # print 'fastest len', len(test_string) return delta if __name__ == '__main__': print '--- CPU TIMES ---' delta_slow = slow() print 'delta slow: {delta_slow}'.format(delta_slow=delta_slow) delta_fast = fast() print 'delta fast: {delta_fast}'.format(delta_fast=delta_fast) delta_fastest = fastest() print 'delta fastest: {delta_fastest}'.format(delta_fastest=delta_fastest) print '---' print 'listcomps is %f times faster than (list.append + ''.join())' % \ (delta_fast/delta_fastest) print 'the latter is %f times faster (slower) than simple concat' %\ (delta_slow/delta_fast)