[Numpy-discussion] numpy.ndarray constructor from python list: bug?
Robin
robince@gmail....
Thu Mar 6 07:21:06 CST 2008
On Thu, Mar 6, 2008 at 9:53 AM, Emanuele Olivetti
<emanuele@relativita.com> wrote:
> Dear all,
>
> Look at this little example:
> ----
> import numpy
> a = numpy.array([1])
> b = numpy.array([1,2,a])
> c = numpy.array([a,1,2])
> ----
> Which has the following output:
> ----
> Traceback (most recent call last):
> File "b.py", line 4, in <module>
> c = numpy.array([a,1,2])
> ValueError: setting an array element with a sequence.
> ----
>
> It seems that a list starting with an ndarray ('a', of
> a single number) is not a legal input to build an ndarray.
> Instead if 'a' is in other places of the list the ndarray
> builds up flawlessly.
>
> Is there a meaning for this behavior or is it a bug?
>
> Details: numpy 1.04 on ubuntu linux x86_64
Hi,
I see the same behaviour with 1.0.5.dev4786. I think the bug is that
the b assignment should also fail. They both fail (as I think they
should) if you take a as an array with more than one element.
I think the array constructor expects lists of numbers, not of arrays
etc. To do what you want try
b = r_[1,2,a]
c = r_[a,1,2]
which works for a an array (and of more than one element).
Cheers
Robin
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