On Sa, 2014-08-30 at 09:04 +0100, Sebastian Berg wrote:
> On Fr, 2014-08-29 at 22:10 -0400, Benjamin Root wrote:
> > Consider the following:
> >
> > a = np.array([(1, 'a'), (2, 'b'), (3, 'c')], dtype=[('foo', 'i'),
> > ('bar', 'a1')])
> >
> > b = np.append(a, (4, 'd'))
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in <module>
> > File
> > "/home/ben/miniconda/lib/python2.7/site-packages/numpy/lib/function_base.py",
> > line 3555, in append
> > return concatenate((arr, values), axis=axis)
> > TypeError: invalid type promotion
> > b = np.insert(a, 4, (4, 'd'))
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in <module>
> > File
> > "/home/ben/miniconda/lib/python2.7/site-packages/numpy/lib/function_base.py",
> > line 3464, in insert
> > new[slobj] = values
> > ValueError: could not convert string to float: d
> >
>
Actually, for insert it is easy to fix
(https://github.com/numpy/numpy/pull/5022), for append there are some
difficulties, because the dtype is not forced to be the arrays dtype,
but gotten from both the original and the appended value currently.
- Sebastian
> Ooops, nice bug in there, might have been me :) (will open a PR).
>
> - Sebastian
>
> >
> > In my original code snippet I was developing which has a more involved
> > dtype, I actually got a different exception:
> > b = np.append(a, c)
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in <module>
> > File
> > "/home/ben/miniconda/lib/python2.7/site-packages/numpy/lib/function_base.py",
> > line 3553, in append
> > values = ravel(values)
> > File
> > "/home/ben/miniconda/lib/python2.7/site-packages/numpy/core/fromnumeric.py",
> > line 1367, in ravel
> > return asarray(a).ravel(order)
> > File
> > "/home/ben/miniconda/lib/python2.7/site-packages/numpy/core/numeric.py",
> > line 460, in asarray
> > return array(a, dtype, copy=False, order=order)
> > ValueError: setting an array element with a sequence.
> >
> >
> > Luckily, this works as a work-around:
> > >>> b = np.append(a, np.array([(4, 'd')], dtype=a.dtype))
> > >>> b
> > array([(1, 'a'), (2, 'b'), (3, 'c'), (4, 'd')],
> > dtype=[('foo', 'i'), ('bar', 'S1')])
> >
> >
> >
> > The same happens whether I enclose the value with square bracket or
> > not. I suspect that this array type just wasn't considered when its
> > checking logic was developed. This is with 1.8.2 from miniconda.
> > Should we consider this a bug or are structured arrays just not
> > expected to be modified like this?
> >
> >
> > Cheers!
> >
> > Ben Root
> >
> > _______________________________________________
> > NumPy-Discussion mailing list
> > NumPy-Discussion@scipy.org
> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
>
>
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