[Numpy-discussion] ndarray methods vs numpy module functions
Bob Dowling
rjd4@cam.ac...
Mon Jun 23 03:31:24 CDT 2008
[ I'm new here and this has the feel of an FAQ but I couldn't find
anything at http://www.scipy.org/FAQ . If I should have looked
somewhere else a URL would be gratefully received. ]
What's the reasoning behind functions like sum() and cumsum() being
provided both as module functions (numpy.sum(data, axis=1)) and as
object methods (data.sum(axis=1)) but other functions - and I stumbled
over diff() - only being provided as module functions?
>>> print numpy.__version__
1.1.0
>>> data = numpy.array([[1,2,3],[4,5,6]])
>>> numpy.sum(data,axis=1)
array([ 6, 15])
>>> data.sum(axis=1)
array([ 6, 15])
>>> numpy.diff(data,axis=1)
array([[1, 1],
[1, 1]])
>>> data.diff(axis=1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'numpy.ndarray' object has no attribute 'diff'
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