Numpy – Check If Element is Finite or Not

In this tutorial, we will look at how to check if a value in a Numpy array is finite or not with the help of some examples.

How to test for finiteness in a Numpy array?

You can use the `numpy.isfinite()` function to check (element-wise) if values in a Numpy array are finite or not. The following is the syntax –

```# test for finiteness - pass scaler value or numpy array
np.isfinite(a)```

It returns a boolean value (`True` if the value is finite otherwise `False`) if you pass a scaler value and a 1-D boolean array if you pass an array.

Examples

Let’s now look at some examples of using the above function to test for finiteness.

Example 1 – Check if a number is finite or not using `numpy.isfinite()`

First, let’s pass scaler values to the `numpy.isfinite()` function.

Let’s create three variables – one containing a finite value and the others set to positive and negative infinity respectively and then apply the `numpy.isfinite()` function on each of these values.

```import numpy as np

# create three variables with scaler values
a = 21
b = np.inf
c = -np.inf

# check if finite
print(np.isfinite(a))
print(np.isfinite(b))
print(np.isfinite(c))```

Output:

```True
False
False```

We get `True` as the output for the scaler value `21` and `False` as the output for both the positive and the negative infinity values.

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Example 2 – Element-wise check for finiteness in a Numpy array using `numpy.isfinite()`

If you apply the `numpy.isfinite()` function on an array, it will return a boolean array containing with `True` for values that are finite and `False` for infinity values.

Let’s create a 1-D array and apply the `numpy.isfinite()` function to it.

```# create a numpy array
ar = np.array([1, 2, np.inf, 4, 5, -np.inf, np.inf])
# element-wise check for finite value in ar
np.isfinite(ar)```

Output:

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

We get a boolean array as an output. You can see that in the boolean array we get `True` for only the values that test as finite in the original array.

Summary

In this tutorial, we looked at how we can use the `numpy.isfinite()` function to check if an element is finite or not in a Numpy array. Keep in mind that if you pass a scaler value, it returns a boolean value and if you pass a 1-D array it returns a boolean array.

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