sys.path[:] = glob.glob(os.path.join(WHEEL_DIR, "*.whl")) + sys.path

sys.path = glob.glob(os.path.join(WHEEL_DIR, "*.whl")) + sys.path

>>> timeit('a[:] = a + [1,2]', setup='a=[]', number=20000)
2.111023200035561
>>> timeit('a = a + [1,2]', setup='a=[]', number=20000)
1.0290934000513516