I'm trying to use numpy to manipulate CSV file. I'm looking for feature
similar to relational database. So I come across a class recarray that
seems to meet my need. And then I see other references of structured
array. Are these just different name of the same feature?
Also I encounter a problem trying to access an field by attribute name. I
have
In [303]: arr = np.array([
.....: (1, 2.2, 0.0),
.....: (3, 4.5, 0.0)
.....: ],
.....: dtype=[
.....: ('unit',int),
.....: ('price',float),
.....: ('amount',float),
.....: ]
.....: )
In [304]: data0 = arr.view(recarray)
In [305]: data0.price[0]
Out[305]: 2.2000000000000002
It works fine when I get a price vector and pick the first element of it.
But if instead I select the first row and try to access its price
attribute, it wouldn't work
In [306]: data0[0].price
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
c:\Python26\Lib\site-packages\numpy\<ipython console> in <module>()
AttributeError: 'numpy.void' object has no attribute 'price'
Then I come across an alternative way to build a recarray. In that case
both usage work fine.
In [307]: data1 = np.rec.fromarrays(
.....: [[1,3],[2.2,4.5],[0.0,0.0]],
.....: names='unit,price,amount')
In [309]: data1.price[0]
Out[309]: 2.2000000000000002
In [310]: data1[0].price
Out[310]: 2.2000000000000002
What's going on here?
Wai Yip
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