これら3つは論理的に同等であり、セットを返すと思います{1, 3, 4}：
set(sum(((1, 3), (4,), (1,)), ()))
set(sum([[1, 3], [4], [1]], []))
functools.reduce(operator.or_, ({1, 3}, {4}, {1}), set())
しかし、ipython (python 3.4.0 の v1.2.1) でそれぞれのパフォーマンスを確認しようとすると、timeit マジックが失敗します。
In [1]: from operator import or_; from functools import reduce
In [2]: timeit set(sum([[1, 3], [4], [1]], []))
1000000 loops, best of 3: 604 ns per loop
In [3]: timeit set(sum(((1, 3), (4,), (1,)), ()))
1000000 loops, best of 3: 330 ns per loop
In [4]: timeit reduce(or_, ({1, 3}, {4}, {1}), set())
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-4-83628f6293f3> in <module>()
----> 1 get_ipython().magic('timeit reduce(or_, ({1, 3}, {4}, {1}), set())')
/usr/lib/python3/dist-packages/IPython/core/interactiveshell.py in magic(self, arg_s)
2164 magic_name, _, magic_arg_s = arg_s.partition(' ')
2165 magic_name = magic_name.lstrip(prefilter.ESC_MAGIC)
-> 2166 return self.run_line_magic(magic_name, magic_arg_s)
2167
2168 #-------------------------------------------------------------------------
/usr/lib/python3/dist-packages/IPython/core/interactiveshell.py in run_line_magic(self, magic_name, line)
2085 kwargs['local_ns'] = sys._getframe(stack_depth).f_locals
2086 with self.builtin_trap:
-> 2087 result = fn(*args,**kwargs)
2088 return result
2089
/usr/lib/python3/dist-packages/IPython/core/magics/execution.py in timeit(self, line, cell)
/usr/lib/python3/dist-packages/IPython/core/magic.py in <lambda>(f, *a, **k)
190 # but it's overkill for just that one bit of state.
191 def magic_deco(arg):
--> 192 call = lambda f, *a, **k: f(*a, **k)
193
194 if isinstance(arg, collections.Callable):
/usr/lib/python3/dist-packages/IPython/core/magics/execution.py in timeit(self, line, cell)
929 number = 1
930 for i in range(1, 10):
--> 931 if timer.timeit(number) >= 0.2:
932 break
933 number *= 10
/usr/lib/python3.4/timeit.py in timeit(self, number)
176 gc.disable()
177 try:
--> 178 timing = self.inner(it, self.timer)
179 finally:
180 if gcold:
<magic-timeit> in inner(_it, _timer)
TypeError: unsupported operand type(s) for |: 'set' and 'tuple'
何が起きてる？2.7 でも失敗します。timeit.timeitバニラの pythonメソッド を使用してこれを再現することはできません。