How to concatenate two arrays in NumPy

You can concatenate two arrays in NumPy with the following code. If you want to learn Python, I highly recommend reading This Book.

Example 1

In this example, I will concatenate two arrays row-wise.

# Import NumPy library
import numpy as np

# Make NumPy arrays
a = np.array([[5, 10], 
              [15, 20]])
b = np.array([[100, 200]])

# Concatenate arrays row wise
print(np.concatenate((a, b), axis=0))

Python
​x
 
# Import NumPy libraryimport numpy as np​# Make NumPy arraysa = np.array([[5, 10],               [15, 20]])b = np.array([[100, 200]])​# Concatenate arrays row wiseprint(np.concatenate((a, b), axis=0))

Output:

[[  5  10]
 [ 15  20]
 [100 200]]

Example 2

In this example, I will concatenate two arrays column-wise.

# Import NumPy library
import numpy as np

# Make NumPy arrays
a = np.array([[5, 10], 
              [15, 20]])
b = np.array([[100, 200]])

# Concatenate arrays Column wise
print(np.concatenate((a, b.T), axis=1))

Python
 
# Import NumPy libraryimport numpy as np​# Make NumPy arraysa = np.array([[5, 10],               [15, 20]])b = np.array([[100, 200]])​# Concatenate arrays Column wiseprint(np.concatenate((a, b.T), axis=1))

Output:

[[  5  10 100]
 [ 15  20 200]]

Example 3

# Import NumPy library
import numpy as np

# Make NumPy arrays
a = np.array([[5, 10], 
              [15, 20]])
b = np.array([[100, 200]])

# Concatenate arrays
print(np.concatenate((a, b), axis=None))

Python
 
# Import NumPy libraryimport numpy as np​# Make NumPy arraysa = np.array([[5, 10],               [15, 20]])b = np.array([[100, 200]])​# Concatenate arraysprint(np.concatenate((a, b), axis=None))