How To Concatenate Arrays in Python [With Examples]

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This post was last Updated on June 14, 2022 by Himanshu Tyagi to reflect the accuracy and up-to-date information on the page.

In this article, we will discuss how to concatenate arrays in Python. An array is a data structure that will store the same data type elements. In Python, we can create an array using the NumPy module.

NumPy stands for numeric Python used to process the arrays. We can create an array in numpy and reverse the array using some inbuilt functions available in NumPy.

Also ReadHow to Create an Empty Array In Python

Syntax:

`import numpy`

Creation:

We can create an array through the NumPy module.

Syntax:

`numpy.array([elements])`

We can also consider a list array in Python.

How to Concatenate Arrays in Python

Python list is a data structure that stores elements with multiple data types. We can create a list by using [].

Let’s see different scenarios to concatenate arrays in Python.

Method 1: Concatenate numpy arrays using concatenate()

In this case, we will concatenate two/more numpy arrays using concatenate() method.

Syntax:

`numpy.concatenate([array1,array2,.....,array n])`

where, array1, array2,.,array n are the arrays to be concatenated.

Example 1:

In this example, we will concatenate two arrays with integer elements

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#display
print(array1)

#display
print(array2)

print("After concatenating")

#concatenate two arrays
print(numpy.concatenate([array1,array2]))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
After concatenating
[ 23  45  67 879  76   5  56  67  65  43]```

Example 2:

In this example, we will concatenate three arrays with integer elements.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#create third  array
array3=numpy.array([1,2,3,4,5])

#display
print(array1)

#display
print(array2)

#display
print(array3)

print("After concatenating")

#concatenate two arrays
print(numpy.concatenate([array1,array2,array3]))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
[1 2 3 4 5]
After concatenating
[ 23  45  67 879  76   5  56  67  65  43   1   2   3   4   5]```

Method 2: Concatenate lists  using the + operator

In this case, we will concatenate two/more lists using the + operator

Syntax:

`array1+array2+.......+array n`

Where, array1, array2,.,array n are the arrays to be concatenated.

Example 1:

In this example, we will concatenate two arrays with integer elements.

```#create first array
array1=[23,45,67,879,76]

#create second array
array2=[5,56,67,65,43]

#display
print(array1)

#display
print(array2)

print("After concatenating")

#concatenate two arrays
print(array1+array2)```

Output:

```[23, 45, 67, 879, 76]
[5, 56, 67, 65, 43]
After concatenating
[23, 45, 67, 879, 76, 5, 56, 67, 65, 43]```

Example 2:

In this example, we will concatenate three arrays with integer elements.

```#create first array
array1=[23,45,67,879,76]

#create second array
array2=[5,56,67,65,43]

#create third  array
array3=[1,2,3,4,5]

#display
print(array1)

#display
print(array2)

#display
print(array3)

print("After concatenating")

#concatenate two arrays
print(array1+array2+array3)```

Output:

```[23, 45, 67, 879, 76]
[5, 56, 67, 65, 43]
[1, 2, 3, 4, 5]
After concatenating
[23, 45, 67, 879, 76, 5, 56, 67, 65, 43, 1, 2, 3, 4, 5]```

Method 3: Concatenate NumPy arrays horizontally

We will concatenate two/more numpy arrays horizontally using the hstack() method.

Syntax:

`numpy.hstack((array1,array2,.....,array n))`

Where, array1, array2,.,array n are the arrays to be concatenated.

Example 1:

In this example, we will concatenate two arrays with integer elements.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#display
print(array1)

#display
print(array2)

print("After concatenating")

#concatenate  arrays
print(numpy.hstack((array1,array2)))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
After concatenating
[ 23  45  67 879  76   5  56  67  65  43]```

Example 2:

In this example, we will concatenate three arrays with integer elements.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#create third  array
array3=numpy.array([1,2,3,4,5])

#display
print(array1)

#display
print(array2)

#display
print(array3)

print("After concatenating")

#concatenate  arrays
print(numpy.hstack((array1,array2,array3)))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
[1 2 3 4 5]
After concatenating
[ 23  45  67 879  76   5  56  67  65  43   1   2   3   4   5]```

Method 4: Concatenate NumPy arrays vertically

We will vertically concatenate two/more numpy arrays using the vstack() method.

Syntax:

`numpy.vstack((array1,array2,.....,array n))`

Where, array1, array2,.,array n are the arrays to be concatenated.

Example 1:

In this example, we will concatenate two arrays with integer elements.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#display
print(array1)

#display
print(array2)

print("After concatenating")

#concatenate  arrays
print(numpy.vstack((array1,array2)))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
After concatenating
[[ 23  45  67 879  76]
[  5  56  67  65  43]]```

Example 2:

In this example, we will concatenate three arrays with integer elements.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#create third  array
array3=numpy.array([1,2,3,4,5])

#display
print(array1)

#display
print(array2)

#display
print(array3)

print("After concatenating")

#concatenate  arrays
print(numpy.vstack((array1,array2,array3)))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
[1 2 3 4 5]
After concatenating
[[ 23  45  67 879  76]
[  5  56  67  65  43]
[  1   2   3   4   5]]```

Method 5: Concatenate numpy arrays by column

In this case, we will concatenate two/more numpy arrays by column using the column_stack() method.

Syntax:

`numpy.column_stack((array1,array2,.....,array n))`

Where, array1, array2,.,array n are the arrays to be concatenated.

Example 1:

In this example, we will concatenate two arrays with integer elements.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#display
print(array1)

#display
print(array2)

print("After concatenating")

#concatenate  arrays
print(numpy.column_stack((array1,array2)))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
After concatenating
[[ 23   5]
[ 45  56]
[ 67  67]
[879  65]
[ 76  43]]```

Example 2:

In this example, we will concatenate three arrays with integer elements.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#create third  array
array3=numpy.array([1,2,3,4,5])

#display
print(array1)

#display
print(array2)

#display
print(array3)

print("After concatenating")

#concatenate  arrays
print(numpy.column_stack((array1,array2,array3)))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
[1 2 3 4 5]
After concatenating
[[ 23   5   1]
[ 45  56   2]
[ 67  67   3]
[879  65   4]
[ 76  43   5]]```

Also ReadHow To Create Keylogger In Python

Method 6: Concatenate arrays in a loop

Here we are using a for loop to iterate over the second array, and by using the append() function, we can add the second array to the first array.

Example:

In this example, we will concatenate two arrays using the append() function through for loop.

```#create first array
array1=[23,45,67,879,76]

#create second array
array2=[5,56,67,65,43]

#display
print(array1)

#display
print(array2)

#use for loop to apped second array to first array

for i in array2:
array1.append(i)

print("After concatenating")
#display the concatenated array
print(array1)```

Output:

```[23, 45, 67, 879, 76]
[5, 56, 67, 65, 43]
After concatenating
[23, 45, 67, 879, 76, 5, 56, 67, 65, 43]```

Method 7: Concatenate arrays of strings

Here we will concatenate the array of strings by using numpy.char() method. And, add() is used to add the two string arrays.

Syntax:

`numpy.char.add(array1,array2)`

Where array1 is the first array, and array2 is the second array.

Example:

In this example, we will concatenate two string arrays.

```#importing the numpy module
import numpy

#create first array
array1=numpy.array(["PHP","R"])

#create second array
array2=numpy.array(["java","jsp"])

#display
print(array1)

#display
print(array2)

print("After concatenating")

#concatenate  arrays

Output:

```['PHP' 'R']
['java' 'jsp']
After concatenating
['PHPjava' 'Rjsp']```

Method 8: concatenate arrays along the axis

Here we will concatenate the array of strings by using numpy.stack() function and concatenate along the row axis and column axis. The row axis is represented by 0, and the column axis is represented by 1.

Syntax:

`numpy.stack((array1,array2,..array n),axis)`

Example 1:

In this example, we will concatenate two integer arrays by row axis.

```import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#display
print(array1)

#display
print(array2)

print("After concatenating")

#display the concatenated array
print(numpy.stack((array1,array2),axis=0))```

Output:

```[23, 45, 67, 879, 76]
[5, 56, 67, 65, 43]
After concatenating
[[ 23  45  67 879  76]
[  5  56  67  65  43]]```

Also ReadHow To Display A Calendar In Python

Example 2:

In this example, we will concatenate two integer arrays by column axis.

```import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#display
print(array1)

#display
print(array2)

print("After concatenating")

#display the concatenated array
print(numpy.stack((array1,array2),axis=1))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
After concatenating
[[ 23   5]
[ 45  56]
[ 67  67]
[879  65]
[ 76  43]]```

Example 3:

In this example, we will concatenate three integer arrays by column axis.

```import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#create third array
array3=numpy.array([1,1,0,1,1])
#display
print(array1)

#display
print(array2)

#display
print(array3)

print("After concatenating")

#display the concatenated array
print(numpy.stack((array1,array2,array3),axis=1))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
[1 1 0 1 1]
After concatenating
[[ 23   5   1]
[ 45  56   1]
[ 67  67   0]
[879  65   1]
[ 76  43   1]]```

Example 4:

In this example, we will concatenate three integer arrays by row axis.

```import numpy

#create first array
array1=numpy.array([23,45,67,879,76])

#create second array
array2=numpy.array([5,56,67,65,43])

#create third array
array3=numpy.array([1,1,0,1,1])
#display
print(array1)

#display
print(array2)

#display
print(array3)

print("After concatenating")

#display the concatenated array
print(numpy.stack((array1,array2,array3),axis=0))```

Output:

```[ 23  45  67 879  76]
[ 5 56 67 65 43]
[1 1 0 1 1]
After concatenating
[[ 23  45  67 879  76]
[  5  56  67  65  43]
[  1   1   0   1   1]]```

Method 9: Concatenate two different size arrays

We can concatenate different size arrays by using the + operator.

Example 1:

In this example, we will create two arrays of different sizes and concatenate them using the + operator.

```#create first array
array1=[23]

#create second array
array2=[5,56,67,65,43]

#display
print(array1)

#display
print(array2)

print("After concatenating")

#display the concatenated array
print(array1+array2)```

Output:

```[23]
[5, 56, 67, 65, 43]
After concatenating
[23, 5, 56, 67, 65, 43]```

Example 2:

In this example, we will create five arrays of different sizes and concatenate them using the + operator.

```#create first array
array1=[23]

#create second array
array2=[5,56,67,65,43]

#create third array
array3=[0,1,2,3,4,5,6,7,8,8,67]

#create forth array
array4=[5,56]

#create fifth array
array5=[5,56,67,65]

#display
print(array1)

#display
print(array2)

#display
print(array3)

#display
print(array4)

#display
print(array5)

print("After concatenating")

#display the concatenated array
print(array1+array2+array3+array4+array5)```

Output:

```[23]
[5, 56, 67, 65, 43]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 67]
[5, 56]
[5, 56, 67, 65]
After concatenating
[23, 5, 56, 67, 65, 43, 0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 67, 5, 56, 5, 56, 67, 65]
```

Also ReadHow to Create Python Empty Set

Method 10: concatenate two arrays with extend()

You can use the extend() Python function to add the second array to the first array.

Syntax:

`array1.extend(array2)`

Example:

In this example, we will concatenate the two arrays using extend() function.

```#create first array
array1=[23]

#create second array
array2=[5,56,67,65,43]

#display
print(array1)

#display
print(array2)

print("After concatenating")

array1.extend(array2)
#display the concatenated array
print(array1)```

Output:

```[23]
[5, 56, 67, 65, 43]
After concatenating
[23, 5, 56, 67, 65, 43]```

Summary

This article discussed ten scenarios to concatenate two or more arrays in Python. We discussed how to concatenate row-wise and column-wise. We also discussed concatenating arrays horizontally and vertically using hstack() and vstack() methods that are available in the NumPy module.

Hello Friends! I am Himanshu, a hobbyist programmer, tech enthusiast, and digital content creator. Founder Cool SaaS Hunter. With CodeItBro, my mission is to promote coding and help people from non-tech backgrounds to learn this modern-age skill!