# Find the First Index of Element in NumPy Array

Manav Narula Nov 26, 2021 Apr 09, 2021 NumPy NumPy Index

In this tutorial, we will discuss how to find the first index of an element in a numpy array.

## Use the `where()` Function to Find the First Index of an Element in a NumPy Array

The `where()` function from the numpy module is used to return an array that contains the indices of elements that satisfy some conditions. The condition is specified within the function.

We can use it to find the first index of a specific value in an array, as shown below.

``````a = np.array([7,8,9,5,2,1,5,6,1])

print(np.where(a==1)[0][0])
``````

Output:

``````5
``````

## Use the `nonzero()` Function to Find the First Index of an Element in a NumPy Array

The `nonzero()` function returns the indices of all the non-zero elements in a numpy array. It returns tuples of multiple arrays for a multi-dimensional array.

Similar to the `where()` function, we can specify the condition also so it can also return the position of a specific element.

For example,

``````a = np.array([7,8,9,5,2,1,5,6,1])

print(np.nonzero(a==1)[0][0])
``````

Output:

``````5
``````

For the most basic purposes, the `where()` and `nonzero()` functions seem similar. The difference arises with the `where()` function when you wish to pick elements of from array `a` if some condition is `True` and from array `b` when that condition is `False`.

## Use the `argmax()` Function to Find the First Index of an Element in a NumPy Array

The `numpy.argmax()` function finds the index of the maximum element in an array. We can specify the equality condition in the function and find the index of the required element also.

For example,

``````a = np.array([7,8,9,5,2,1,5,6,1])

print(np.argmax(a==1))
``````

Output:

``````5
``````

## Use the `index()` Function to Find the First Index of an Element in a NumPy Array

In this method, we will first convert the array to a list using the `tolist()` function. Then we will use the `index()` function, which will return the position of the specified element.

The following code implements this.

``````a = np.array([7,8,9,5,2,1,5,6,1])

print(a.tolist().index(1))
``````

Output:

``````5
``````
Author: Manav Narula

Manav is a IT Professional who has a lot of experience as a core developer in many live projects. He is an avid learner who enjoys learning new things and sharing his findings whenever possible.