[PYTHON] NumPy zeros can be defined even with a size of 0

Overview

--NumPy allows you to define zeros of size 0 like np.zeros ((0, 4)) --With this, you can also define an empty list and add it with append () with array.

I want to do something like list.append () with NumPy array

List can use append

What I often do when creating lists in Python

a = []
for i in range(10):
    a.append(1)

Someone like

Array has no append

If you try to do the same with a NumPy Array, you'll end up using numpy.vstack () or numpy.hstack () → Since the number of rows (or columns) of the two Arrays to be attached must match, we first defined an Array with shape = (1, 4).

Bad person


import numpy as np
a = np.zeros((1, 4))
for i in range(10):
    ones = np.ones((1, 4))
    a = a.vstack((a, ones))
a = a[1:, :] #Only the first defined part is excluded

Array of size 0 can be defined

I felt uncomfortable with the operation of defining an Array of shape = (1, 4) first and then removing it, so I had to define zeros of size 0 as a trial.

Easy to see


import numpy as np
a = np.zeros((0, 4)) #Zero size zeros
for i in range(10):
    ones = np.ones((1, 4))
    a = a.vstack((a, ones))


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