How to include the first few items of a numpy array with python

Question

I have array d, I want array d2 The rows do not have the same number of items.

 d=   [ ['q', 'u', 's', 'a', 'p', 'e', 'a']
     ['500', 'G', 'G', 'C', 'C', 'P', '04/12/2011', '' ]
     ['500', 'G', 'G', 'F', 'C', 'P', '04/12/2011', ''] 
     ['5', 'ZUMZ', 'ZUMZ', 'C', 'C', 'B', '04/12/2011', '']
     ['2', 'ZUMZ', 'ZUMZ', 'F', 'C', 'B', '04/12/2011', '']
     ['7', 'ZUMZ', 'ZUMZ', 'M', 'C', 'B', '04/12/2011', '']]

Only the first five itmes.

 d2=   [ ['q', 'u', 's', 'a', 'p']
         ['500', 'G', 'G', 'C', 'C']
         ['500', 'G', 'G', 'F', 'C'] 
         ['5', 'ZUMZ', 'ZUMZ', 'C', 'C']
         ['2', 'ZUMZ', 'ZUMZ', 'F', 'C']
         ['7', 'ZUMZ', 'ZUMZ', 'M', 'C']]


f = urllib.urlopen(url)
f = csv.reader(f)
d= np.asarray(list(f), dtype= 'object')
print d
m=  d[:,:]                
print m

I tried above and m= d[:,0:5]

m= d[:,0:5] should return exactly first five columns of an array. what do you get instead? — Andrey Sboev
– Andrey Sboev, Commented Apr 14, 2011 at 12:49
@user428862 and @Andrey: The issue is that if your list of lists is (N,M) and you use the object dtype, you get an (N,) array, where each element is a list, rather than an array of M elements. — JoshAdel
– JoshAdel, Commented Apr 14, 2011 at 13:29

JoshAdel · Accepted Answer · 2011-04-14 12:46:22Z

1

How about:

m = np.array([x[:5] for x in d], dtype=object)

Although if they are all strings, you should use a string dtype instead.

answered Apr 14, 2011 at 12:46

JoshAdel

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2 Comments

JoshAdel Over a year ago

@user428862: I didn't mean dtype=string, rather a string dtype, which would be something like dtype='S8' or dtype=(str,16), etc.

Merlin Over a year ago

oh, thanks, would there be a pick in speed, likely more compact, right?

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