myl = myl1
t1 = timeit.Timer('UsePlus()', 'from __main__ import UsePlus')
t2 = timeit.Timer('UseJoin()', 'from __main__ import UseJoin')
print('%.2f usec/pass' % (1000000 * t1.timeit(number=100000) / 100000))
print('%.2f usec/pass' % (1000000 * t2.timeit(number=100000) / 100000))
Any reason not to use '+' to concatenate two strings?