Python - How to concatenate more than arrays lists in python?

Question

I have many arrays, let's say

X = np.array([1, 2, 3, 4])
Y = np.array([5, 6, 7, 8])
Z = np.array([9, 10, 11, 12])

I want to concatenate them all so I have

arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

Here is what I've tried

arr = X + Y + Z

this doesn't work, here is my result

>>> print(arr)
[15, 18, 21, 24]

Just the sum of each element at an index i. Any suggestions?

Can't reproduce, your code works for me. Also, don't call your list list, it masks the built-in type — sacuL
– sacuL, Commented Oct 12, 2018 at 3:13
are you sure they're lists? X + Y + Z should give you what you want. — jedwards
– jedwards, Commented Oct 12, 2018 at 3:14
Based on the results, you "lists" are not lists but numpy array. Please confirm. — DYZ
– DYZ, Commented Oct 12, 2018 at 3:15
@DYZ just checked the type. You are right, it is not a list, but a numpy array. I'll edit the question now — AlexT
– AlexT, Commented Oct 12, 2018 at 3:18

R.A.Munna · Accepted Answer · 2018-10-12 03:22:28Z

1

you can use np.concatenate()

a = np.concatenate((X, Y, Z))
print(a)
[ 1  2  3  4  5  6  7  8  9 10 11 12]

answered Oct 12, 2018 at 3:22

R.A.Munna

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Comments

bunbun · Accepted Answer · 2018-10-12 03:23:45Z

0

Use np.concatenate to combine np arrays:

import numpy as np 
X = np.array([1, 2, 3, 4])
Y = np.array([5, 6, 7, 8])
Z = np.array([9, 10, 11, 12])

print np.concatenate((X,Y,Z), axis=0)

answered Oct 12, 2018 at 3:23

bunbun

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