Numpy – Get the Number of Rows of an Array

In this tutorial, we will look at how to get the number of rows of a 2D array in Numpy with the help of some examples.

How to get the number of rows in Numpy?

You can use the Python built-in len() function or the numpy.ndarray.shape property to get the number of rows of a 2d Numpy array.

The following is the syntax –

# num rows using the len() function
len(ar)
# num rows using the .shape property
ar.shape[0]

Let’s now look at both the methods with the help of some examples –

First, we will create a 2d Numpy array that we will be using throughout this tutorial.

import numpy as np

# create a 2d array
ar = np.array([
    [1, 2, 3, 4],
    [1, 1, 0, 0],
    [5, 6, 7, 8]
])
# display the array
print(ar)

Output:

[[1 2 3 4]
 [1 1 0 0]
 [5 6 7 8]]

Here, we used the numpy.array() function to create a 2d array with three rows and four columns.

Method 1 – Number of rows using the len() function

len() is a Python built-in function that returns the length of an object. It is used on sequences or collections. If you apply the len() function on a 2d Numpy array, it will return the number of rows in the array.

# number of rows of array
print(len(ar))

Output:

3

We get the number of rows in the above array as 3.

Method 2 – Number of rows using the .shape property

You can also get the number of rows in a 2d Numpy array by accessing its .shape property which returns the tuple (row_count, column_count). To only get the row count, access the value at the index 0 from the shape property.

# number of rows of array
print(ar.shape[0])

Output:

3

We get the same result as above, 3.

Summary

In this tutorial, we looked at two methods to get the row count for a 2d array in Numpy.

1. Use the Python built-in len() function.
2. Via the .shape property of the array. (Value at the 0th index of the shape tuple is the row count)

You might also be interested in –

• Numpy – Create a Diagonal Matrix (With Examples)
• Get the First N Rows of a 2D Numpy Array
• Get the Last N Rows of a 2D Numpy Array