Python - Join Arrays

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In Python, array is a homogenous collection of Python's built in data types such as strings, integer or float objects. However, array itself is not a built-in type, instead we need to use the array class in Python's built-in array module.

First Method

To join two arrays, we can do it by appending each item from one array to other.

Here are two Python arrays −

a = arr.array('i', [10,5,15,4,6,20,9])
b = arr.array('i', [2,7,8,11,3,10])

Run a for loop on the array "b". Fetch each number from "b" and append it to array "a" with the following loop statement −

for i in range(len(b)):
   a.append(b[i])

The array "a" now contains elements from "a" as well as "b".

Here is the complete code −

import array as arr
a = arr.array('i', [10,5,15,4,6,20,9])
b = arr.array('i', [2,7,8,11,3,10])
for i in range(len(b)):
   a.append(b[i])
print (a, b)

It will produce the following output −

array('i', [10, 5, 15, 4, 6, 20, 9, 2, 7, 8, 11, 3, 10])

Second Method

Using another method to join two arrays, first convert arrays to list objects −

a = arr.array('i', [10,5,15,4,6,20,9])
b = arr.array('i', [2,7,8,11,3,10])
x=a.tolist()
y=b.tolist()

The list objects can be concatenated with the '+' operator.

z=x+y

If "z" list is converted back to array, you get an array that represents the joined arrays −

a.fromlist(z)

Here is the complete code −

from array import array as arr
a = arr.array('i', [10,5,15,4,6,20,9])
b = arr.array('i', [2,7,8,11,3,10])
x=a.tolist()
y=b.tolist()
z=x+y
a=arr.array('i')
a.fromlist(z)
print (a)

Third Method

We can also use the extend() method from the List class to append elements from one list to another.

First, convert the array to a list and then call the extend() method to merge the two lists −

from array import array as arr
a = arr.array('i', [10,5,15,4,6,20,9])
b = arr.array('i', [2,7,8,11,3,10])
a.extend(b)
print (a)

It will produce the following output −

array('i', [10, 5, 15, 4, 6, 20, 9, 2, 7, 8, 11, 3, 10])