create an empty numpy array and append

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showing results for - "create an empty numpy array and append"

1In [210]: %%timeit
2   .....: l = []
3   .....: for i in xrange(1000):
4   .....:     l.append([3*i+1,3*i+2,3*i+3])
5   .....: l = np.asarray(l)
6   .....: 
71000 loops, best of 3: 1.18 ms per loop
8
9In [211]: %%timeit
10   .....: a = np.empty((0,3), int)
11   .....: for i in xrange(1000):
12   .....:     a = np.append(a, 3*i+np.array([[1,2,3]]), 0)
13   .....: 
14100 loops, best of 3: 18.5 ms per loop
15
16In [214]: np.allclose(a, l)
17Out[214]: True

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