How to make a Structured Array from multiple simple array

Question

import numpy as np

a=np.array([1,2,3,4,5,6,7,8,9])
b=np.array([\"a\",\"b\",\"c\",\"d\",\"e\",\"f\",\"g\",\"h\",\"i\"])
c=np.array([9,8,7,6,5,4,3,2,1])
datatype=np.d         


        

Answer 1

You might as well try numpy.rec.fromarrays.

import numpy as np

a=np.array([1,2,3,4,5,6,7,8,9])
b=np.array(["a","b","c","d","e","f","g","h","i"])
c=np.array([9,8,7,6,5,4,3,2,1])

d = np.rec.fromarrays([a,b,c], formats=['i','S32','i'], names=['num','char','len'])

Although timings are not as good as using itertools.

In [2]: %timeit d = np.rec.fromarrays([a,b,c], formats=['i','S32','i'], names=['num','char','len'])
10000 loops, best of 3: 86.5 us per loop

In [6]: import itertools

In [7]: %timeit np.fromiter(itertools.izip(a,b,c),dtype=datatype)
100000 loops, best of 3: 11.5 us per loop