create an array or list with different element sizes python

Question

I would like to create an array or list with different element size however, I got the output not as expected with a word array written in the middle of the array as in the following:

import numpy as np
lst_2=np.array([1,2,np.repeat(3,3),2],dtype="object")
print(lst_2) 
#Output is=[ 1 2 array([3,3,3]) 2]
#lst_2 should be = [1,2,3,3,3,2]......

please any help or suggestion

sehan2 · Accepted Answer · 2021-10-19 13:01:33Z

1

You are mixing lists and numpy arrays. I presume what you want to achieve is a numpy array that looks as follows:

import numpy as np
lst_2=np.concatenate([np.array([1,2]), np.repeat(3,3),[2]])
print(lst_2)

Output:

[1 2 3 3 3 2]

Alternatively you can also use the following if you want a list:

lst_2 = [1,2] + list(np.repeat(3,3)) + [2]

The plus operator here stands for concatenation of two lists. Whereas the plus operator stands for elementwise addition in case of numpy arrays.

edited Oct 19, 2021 at 13:01

answered Oct 19, 2021 at 9:23

sehan2

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2 Comments

msci Over a year ago

Thank you for your feedback, it works perfectly However, lst_2 will be from an input so I would like to avoid adding np.array, inside each element, Do you have any suggestion or advice, or how could I have an array or list then add [] for each number later ?? Thank you,

hpaulj Over a year ago

keep in mind that + for lists is join, but addition for arrays.

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