```
In [42]: X = list(np.random.RandomState(1).normal(0, 1, (1000, 2000)))

In [43]: timeit y2 = X.sort(key=lambda x: np.sum(x ** 2))
100 loops, best of 3: 17.4 ms per loop

In [44]: X = list(np.random.RandomState(1).normal(0, 1, (1000, 2000)))

In [45]: timeit y1 = X.sort(key=lambda x: sum([x_i ** 2 for x_i in x]))
1 loops, best of 3: 4.58 s per loop
```