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)]