append element to array

Question

I received error while appending element to an array.

array([[ 5,  89,  342,  282,    3,  644, 1254,  634,    4,  711,   58,
        1554,  23,  613,  565,    2,  787,  968,  640,    7,  676,  65,
         346]])

I want to append mean of this array 3 times to this array so if the mean is 10, "10, 10, 10" will be added to the array.

mean = array.mean()
array= array.append(mean, mean, mean)

error message

'numpy.ndarray' object has no attribute 'append'

Where did I do wrong ? thank you

append as you are using it, is meant for lists. Perhaps you want numpy.append? — DavidG
– DavidG, Commented Nov 1, 2018 at 22:03
@DavidG thanks. if i used np.append I got another error message 'append() missing 1 required positional argument: 'values'' — Osca
– Osca, Commented Nov 1, 2018 at 22:05
it obviously isnt if the interpreter is saying there was a problem with a numpy object (where is the import?) — user7451701
– user7451701, Commented Nov 1, 2018 at 22:08

Mahdi Nazari Ashani · Accepted Answer · 2018-11-01 22:11:51Z

1

you should do something like this.

import numpy as np

array = np.array([[ 5,  89,  342,  282,    3,  644, 1254,  634,    4,  711,   58,
        1554,  23,  613,  565,    2,  787,  968,  640,    7,  676,  65,
         346]])

mean = array.mean()

new_array = np.append(array,np.array([mean,mean,mean]))

answered Nov 1, 2018 at 22:11

Mahdi Nazari Ashani

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5 Comments

Mark Quinn Over a year ago

works well on testing. Out of curiousity - do you know why this works using numpy?

Mahdi Nazari Ashani Over a year ago

I'm not sure what you are meaning. I know each object has its own methods. 'numpy' is an object 'array' is another object too. Append is a method for 'numpy' not for 'array'.

Osca Over a year ago

Because array is a mutable object ?

Mark Quinn Over a year ago

I'm confusing append on a list with append on an array - just getting up to scratch on numpy. That helps some - thanks!

Mahdi Nazari Ashani Over a year ago

@takkyi83 I think this is true. if you refer to this address you will find some function are "(numpy.ndarray method)". these function can be used as method of 'array' object. but some of them like 'append' are just "(in module numpy)". so the second one can be available for 'numpy' objects.

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