[Numpy-discussion] dtype names and titles

N. Volbers mithrandir42 at web.de
Sat Feb 11 04:46:02 CST 2006


I continue to learn all about the heterogeneous arrays...

When I was reading through the records.py code I discovered that besides 
the 'names' and 'formats' for the fields of a numpy array you can also 
specify 'titles'. Playing around with this feature I discovered a bug:

 >>> import numpy
 >>> mydata = [(1,1), (2,4), (3,9)]
 >>> mytype = {'names': ['col1','col2'], 'formats':['i2','f4'], 
'titles': ['col2', 'col1']}
 >>> b = numpy.array( mydata, dtype=mytype)
 >>> print b
[(1.0, 1.0) (4.0, 4.0) (9.0, 9.0)]

This seems to be caused by the fact that you can access a field by both 
the name and the field title. Why would you want to have two names anyway?

By the way, is there an easy way to access a field vector by its index? 
Right now I retrieve the field name from dtype.fields[-1][index] and 
then return the 'column' by using myarray[name].

Best regards,

Niklas.





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