[Numpy-discussion] Syntax equivalent for np.array()

Gökhan Sever gokhansever@gmail....
Wed Feb 10 10:24:34 CST 2010


On Wed, Feb 10, 2010 at 10:12 AM, Gökhan Sever <gokhansever@gmail.com>wrote:

>
>
> On Wed, Feb 10, 2010 at 10:06 AM, Angus McMorland <amcmorl@gmail.com>wrote:
>
>> On 10 February 2010 11:02, Gökhan Sever <gokhansever@gmail.com> wrote:
>> > Hi,
>> >
>> > Simple question:
>> >
>> > I[4]: a = np.arange(10)
>> >
>> > I[5]: b = np.array(5)
>> >
>> > I[8]: a*b.cumsum()
>> > O[8]: array([ 0,  5, 10, 15, 20, 25, 30, 35, 40, 45])
>> >
>> > I[9]: np.array(a*b).cumsum()
>> > O[9]: array([  0,   5,  15,  30,  50,  75, 105, 140, 180, 225])
>> >
>> > Is there a syntactic equivalent for the I[9] --for instance instead of
>> using
>> > "list" keyword I use [ ] while creating a list. Is there a shortcut for
>> > np.array instead of writing np.array(a*b) explicitly?
>>
>> How about just (a*b).cumsum() ?
>>
>> Angus.
>> --
>> AJC McMorland
>> Post-doctoral research fellow
>> Neurobiology, University of Pittsburgh
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>> NumPy-Discussion@scipy.org
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>>
>
> Yep that's it :) I knew that it was a very simple question.
>
> What confused me is I remember somewhere not sure maybe in IPython dev I
> have gotten when I do:
>
> (a*b).cumsum()
>
> AttributeError: 'tuple' object has no attribute 'cumsum' error.
>
> So I was thinking ( ) is a ssugar for tuple and np.array might have
> something special than these.
>
> --
> Gökhan
>

Self-correction:

It works correctly in IPython-dev as well.

And further in Python 2.6.2:

>>> p = ()
>>> p
()
>>> type(p)
<type 'tuple'>
>>> type((a*b))
<type 'numpy.ndarray'>

( ) doesn't only works as a tuple operator. It also has its original
parenthesis functionality :)

-- 
Gökhan
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