strappendtest.py

import string, random
from timeit import Timer

strs = []

for i in range(500):
    strs.append(''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(10)))

def slow():
    str = ''
    for s in strs:
        str +=s

def fast():
    str = ''.join(strs)

t = Timer(lambda: slow())
print t.timeit(number=100000)

t = Timer(lambda: fast())
print t.timeit(number=100000)