[Numpy-discussion] Creating an ndarray from an iterable over sequences

[Dr. Leo]

Hi,

I would like to write something like:

In [25]: iterable=((i, i**2) for i in range(10))

In [26]: a=np.fromiter(iterable, int32)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call
last)
<ipython-input-26-5bcc2e94dbca> in <module>()
----> 1 a=np.fromiter(iterable, int32)

ValueError: setting an array element with a sequence.


Is there an efficient way to do this?

Creating two 1-dimensional arrays first is costly as one has to
iterate twice over the data. So the only way I see is creating an
empty [10,2] array and filling it row by row. This is memory-efficient
but slow. List comprehension is vice versa.

If there is no solution, wouldn't it be possible to rewrite fromiter
so as to accept sequences?

Leo