Python Add an Item to an Array

Question

I have an ndarray that looks like this:

In  [1]: a
Out [1]: array(['x','y'], dtype=object)

Now I wanted to append a "z" to the end of it:

In  [2]: print([a,'z'])
[array(['x','y'],dtype=object), 'z']

Instead, what I want is:

['x','y','z']

Any idea?

akuiper · Accepted Answer · 2017-02-22 15:13:35Z

11

You can do it using numpy.append:

import numpy as np

a = np.array(['x','y'])

b = np.append(a,['z'])

In [8]:b
Out[8]: array(['x', 'y', 'z'], dtype='<U1')

akuiper

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answered Feb 22, 2017 at 15:12

Wenlong Liu

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Comments

akuiper · Accepted Answer · 2017-02-22 15:11:57Z

1

You can use numpy.append:

import numpy as np
a = np.array(['x', 'y'])

np.append(a, 'z')
# array(['x', 'y', 'z'], 
#       dtype='<U1')

answered Feb 22, 2017 at 15:11

akuiper

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armatita · Accepted Answer · 2017-02-22 15:15:39Z

0

As alternative to append (since you can use it for several iterables; check for example: PEP3132) you can use the "unpacking" symbol to do it:

import numpy as np

a = np.array(['x','y'], dtype=object)
b = np.array([*a, "z"])
print(*a, "z")
print(b)

The result is this:

x y z
['x' 'y' 'z']

answered Feb 22, 2017 at 15:15

armatita

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