Add rows to an empty array with numpy

Postscript: I'm a beginner, so I don't know how to use NumPy at all lol Instead of creating and combining Numpy arrays in a loop All you have to do is create a multidimensional list and finally convert it with np.array (). Easy to implement and fast to operate.

In short, I wanted to do something like the article below. https://kakedashi-engineer.appspot.com/2020/02/28/multi-list-numpy/

Whole source code

numpy_join.py


# coding:UTF-8
import numpy as np
a = np.zeros((0,3))
for i in range(5):
    b = np.array([1, 2, 3])
    a = np.r_[a,b.reshape(1,-1)]
print a

I want to make a two-dimensional array in the end, so in this way

python


a = np.zeros((0,3))

The point is to do like this. The number of elements in one row is 3, and a two-dimensional array with 0 rows is created. You can use np.empty, but since it has 0 lines anyway, I dared to use np.zeros.

continue

python


a = np.r_[a,b.reshape(1,-1)]

However, note that b is reshaped to make a two-dimensional array.

result


[[ 1.  2.  3.]
 [ 1.  2.  3.]
 [ 1.  2.  3.]
 [ 1.  2.  3.]
 [ 1.  2.  3.]]

The desired result was obtained.

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