Performance comparison: insert vs build Python set operations

Question

In python, is it faster to a) Build a set from a list of n items b) Insert n items into a set?

I found this page (http://wiki.python.org/moin/TimeComplexity) but it did

Answer 1

On my Thinkpad:

In [37]: timeit.timeit('for a in x: y.add(a)',
                       'y=set(); x=range(10000)', number=10000)
Out[37]: 12.18006706237793

In [38]: timeit.timeit('y=set(x)', 'y=set(); x=range(10000)', number=10000)
Out[38]: 3.8137960433959961