Python array to 1-D Vector

Question

Is there a pythonic way to convert a structured array to vector?

For example:

I'm trying to convert an array like:

[(9,), (1,), (1, 12), (9,), (8,)]

to a vector like:

[9,1,1,12,9,8]

This doesn't actually look like numpy.

user2357112
– user2357112

2013-08-04 23:34:24 +00:00
Commented Aug 4, 2013 at 23:34 — user2357112
– user2357112, Commented Aug 4, 2013 at 23:34

unutbu · Accepted Answer · 2016-11-02 13:18:18Z

14

In [15]: import numpy as np

In [16]: x = np.array([(9,), (1,), (1, 12), (9,), (8,)])

In [17]: np.concatenate(x)
Out[17]: array([ 9,  1,  1, 12,  9,  8])

Another option is np.hstack(x), but for this purpose, np.concatenate is faster:

In [14]: x = [tuple(np.random.randint(10, size=np.random.randint(10))) for i in range(10**4)]

In [15]: %timeit np.hstack(x)
10 loops, best of 3: 40.5 ms per loop

In [16]: %timeit np.concatenate(x)
100 loops, best of 3: 13.6 ms per loop

edited Nov 2, 2016 at 13:18

answered Aug 4, 2013 at 23:37

unutbu

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Comments

zs2020 · Accepted Answer · 2013-08-05 00:37:00Z

8

You don't need to use any numpy, you can use sum:

myList = [(9,), (1,), (1, 12), (9,), (8,)]
list(sum(myList, ()))

result:

[9, 1, 1, 12, 9, 8]

answered Aug 5, 2013 at 0:37

zs2020

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Comments

PSN · Accepted Answer · 2019-07-20 10:34:41Z

8

Use numpy .flatten() method

>>> a = np.array([[1,2], [3,4]])
>>> a.flatten()
array([1, 2, 3, 4])
>>> a.flatten('F')
array([1, 3, 2, 4])

Source: Scipy.org

answered Jul 20, 2019 at 10:34

PSN

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