The Numpy library in Python comes with a number of useful functions and methods to work with and manipulate the data in arrays. In this tutorial, we will look at how to get all the values in a Numpy array that are smaller than a given value, k with the help of some examples.

## Steps to get all the values smaller than a given value in Numpy

You can use boolean indexing to filter the Numpy array such that the resulting array contains only the elements that specify a given condition. For example, values smaller than k.

### Step 1 – Create a Numpy array

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

import numpy as np # create a numpy array ar = np.array([1, 2, 3, 4, 5, 6, 7]) # display the array print(ar)

Output:

[1 2 3 4 5 6 7]

Here, we used the `numpy.array()`

function to create a one-dimensional Numpy array containing some numbers.

### Step 2 – Filter the array using a boolean expression

To get all the values from a Numpy array smaller than a given value, filter the array using boolean indexing.

First, we will specify our boolean expression, `ar < k`

and then use the boolean array resulting from this expression to filter our original array.

For example, let’s get all the values in the above array that are smaller than 5 (k = 5).

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# values in array smaller than 5 print(ar[ar < 5])

Output:

[1 2 3 4]

We get all the values in the array `ar`

that are smaller than 5.

To understand what’s happening here, let’s look under the hood. Let’s see what we get from the expression `ar < 5`

.

ar < 5

Output:

array([ True, True, True, True, False, False, False])

We get a boolean array. The boolean values in this array represent whether a value at a particular index satisfies the given condition or not (in our case whether the element is smaller than 5 or not).

When we do `ar[ar < 5]`

, we are essentially filtering the original array where the condition evaluates to `True`

.

You can similarly filter a Numpy array for other conditions as well.

## Summary – Get all values smaller than a given value in a Numpy array

In this tutorial, we looked at how to get all the values in a Numpy array that are smaller than a given value. The following is a short summary of the steps mentioned –

- Create a Numpy array (skip this step if you already have an array to operate on).
- Use boolean indexing to filter the array for only the values that are smaller than the given value,
`ar[ar < k]`

.

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