python benchmarks string concat

C:\Users\ronnieaka>python -m timeit -s 's=""' 's+="a"'
100000000 loops, best of 3: 0.0185 usec per loop

C:\Users\ronnieaka>python -m timeit -s 's=[]' 's.append("a")'
100000000 loops, best of 3: 0.0183 usec per loop

C:\Users\ronnieaka>python -m timeit -s 's=""' 's="".join((s,"a"))'
100000000 loops, best of 3: 0.0185 usec per loop

C:\Users\ronnieaka>python -m timeit -s 's=""' 's="%s%s"%(s,"a")'
100000000 loops, best of 3: 0.0183 usec per loop

2.4GHz Intel core 2 duo, Python 2.7.2, Windows Vista 32 bit.