On Fri, May 13, 2011 at 10:58 AM, Bruce Southey <bsout...@gmail.com> wrote: > Hi, > How do you create a 'single' structured array using np.array()? > Basically I am attempting to do something like this that does not work: > a=np.array([1,2, 3,4, 5,6], dtype=np.dtype([('foo', int)])) > > I realize that this is essentially redundant as if A is an 1-d array > then a structured array with a named field 'foo' is the same thing - A > would be A['foo'], just shorter. > > So if that is valid then a clearer error message is required to indicate > this and provide the suitable error message to address ticket 1264 > (http://projects.scipy.org/numpy/ticket/1264). > > $ python > Python 2.7 (r27:82500, Sep 16 2010, 18:02:00) > [GCC 4.5.1 20100907 (Red Hat 4.5.1-3)] on linux2 > Type "help", "copyright", "credits" or "license" for more information. > >>> import numpy as np > >>> a=np.array([1,2, 3,4, 5,6], dtype=np.dtype([('foo', int)])) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: expected a readable buffer object > >>> np.array([(1,2), (3,4), (5,6)], dtype=np.dtype([('foo', int), > ('foo2', int)])) > array([(1, 2), (3, 4), (5, 6)], > dtype=[('foo', '<i8'), ('foo2', '<i8')]) > >>> a=np.array([(1), (3), (5)], dtype=np.dtype([('foo', int)])) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: expected a readable buffer object > >>> np.array([(1), (3), (5)], dtype=np.dtype(int)) > array([1, 3, 5]) > >>> np.array((1,2, 3,4, 5,6)) > array([1, 2, 3, 4, 5, 6])
Using a view works, (and direct assignment of dtype) >>> a=np.array([1,2, 3,4, 5,6]).view(([('foo', int)])) >>> a array([(1,), (2,), (3,), (4,), (5,), (6,)], dtype=[('foo', '<i4')]) >>> b = a.copy() >>> b array([(1,), (2,), (3,), (4,), (5,), (6,)], dtype=[('foo', '<i4')]) >>> a1 = np.array([1,2, 3,4, 5,6]).astype([('foo', int)]) Traceback (most recent call last): File "<pyshell#36>", line 1, in <module> a1 = np.array([1,2, 3,4, 5,6]).astype([('foo', int)]) TypeError: expected a readable buffer object >>> a1 = np.array([1,2, 3,4, 5,6]) >>> a1.dtype dtype('int32') >>> a1.dtype = np.dtype([('foo', int)]) >>> a1 array([(1,), (2,), (3,), (4,), (5,), (6,)], dtype=[('foo', '<i4')]) Josef > > Thanks > Bruce > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion