Python - Join Arrays

---

---

The process of joining two arrays is termed as Merging or concatenating. Python provides multiple ways to merge two arrays such as append() and extend() methods. But, before merging two arrays always ensure that both arrays are of the same data type otherwise program will throw error.

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 Python's built-in array module.

Join two Arrays in Python

To join arrays in Python, use the following approaches −

• Using append() method
• Using + operator
• Using extend() method

Using append() Method

To join two arrays, we can append each item from one array to other using append() method. To perform this operation, run a for loop on the original array, fetch each element and append it to a new array.

Example: Join Two Arrays by Appending Elements

Here, we use the append() method to join two arrays.

import array as arr

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

# merging both arrays
for i in range(len(b)):
   a.append(b[i])
print (a)

It will produce the following output −

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

Using + operator

We can also use + operator to concatenate or merge two arrays. In this approach, we first convert arrays to list objects, then concatenate the lists using the + operator and convert back to get merged array.

Example: Join Two Arrays by Converting to List Objects

In this example, we will see how to join two arrays using + operator.

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', z)
print (a)

The above code will display the following output −

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

Using extend() Method

Another approach to concatenate arrays is the use of extend() method from the List class. Similar to above approach, we first convert the array to a list and then call the extend() method to merge the two lists.

Example: Join Two Arrays using extend() Method

In the following example, we will use the extend() method to concatenate two arrays in Python.

import array as arr
a = arr.array('i', [88, 99, 77, 66, 44, 22])
b = arr.array('i', [12, 17, 18, 11, 13, 10])
a.extend(b)
print (a)

It will produce the following output −

array('i', [88, 99, 77, 66, 44, 22, 12, 17, 18, 11, 13, 10])