[Numpy-discussion] Error using rec.fromrecords with specific dtype

Sameer DCosta sameerslists@gmail....
Thu Aug 7 14:44:37 CDT 2008


Hi,

I am unable to specify a dtype when using numpy.rec.fromrecords. This
problem only occurs when one of the dtypes is an object.  (Please see
below)
Thanks in advance for your help.

Sameer

In [7]: import datetime, numpy as np

In [8]: print np.__version__
1.2.0.dev5253

In [9]: dtype=np.dtype([('spam', '|O4'),('ham', '<i4')] )

In [10]: data = [ (datetime.date(2001,1,1), 2),
(datetime.date(2001,1,2), 4), (datetime.date(2001,1,3), 6) ]

In [11]: n = np.rec.fromrecords(data, dtype=dtype)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

/home/titan/sameer/<ipython console>

/home/titan/sameer/local/mins/lib/python2.4/site-packages/numpy/core/records.pyc
in fromrecords(recList, dtype, shape, formats, names, titles, aligned,
byteorder)
    469     res = retval.view(recarray)
    470
--> 471     res.dtype = sb.dtype((record, res.dtype))
    472     return res
    473

/home/titan/sameer/local/mins/lib/python2.4/site-packages/numpy/core/records.pyc
in __setattr__(self, attr, val)
    287             if attr not in fielddict:
    288                 exctype, value = sys.exc_info()[:2]
--> 289                 raise exctype, value
    290         else:
    291             fielddict =
ndarray.__getattribute__(self,'dtype').fields or {}

TypeError: Cannot change data-type for object array.

In [12]: names = "spam,ham"

In [13]: n = np.rec.fromrecords(data, names=names)

In [14]: print n
[(datetime.date(2001, 1, 1), 2) (datetime.date(2001, 1, 2), 4)
 (datetime.date(2001, 1, 3), 6)]


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