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You can use the following methods to find the index position of specific values in a NumPy array:

**Method 1: Find All Index Positions of Value**

np.where(x==value)

**Method 2: Find First Index Position of Value**

np.where(x==value)[0][0]

**Method 3: Find First Index Position of Several Values**

#define values of interest vals = np.array([value1, value2, value3]) #find index location of first occurrence of each value of interest sorter = np.argsort(x) sorter[np.searchsorted(x, vals, sorter=sorter)]

The following examples show how to use each method in practice.

**Method 1: Find All Index Positions of Value**

The following code shows how to find every index position that is equal to a certain value in a NumPy array:

import numpy as np #define array of values x = np.array([4, 7, 7, 7, 8, 8, 8]) #find all index positions where x is equal to 8 np.where(x==8) (array([4, 5, 6]),)

From the output we can see that index positions 4, 5, and 6 are all equal to the value **8**.

**Method 2: Find First Index Position of Value**

The following code shows how to find the first index position that is equal to a certain value in a NumPy array:

import numpy as np #define array of values x = np.array([4, 7, 7, 7, 8, 8, 8]) #find first index position where x is equal to 8 np.where(x==8)[0][0] 4

From the output we can see that the value **8** first occurs in index position 4.

**Method 3: Find First Index Position of Several Values**

The following code shows how to find the first index position of several values in a NumPy array:

import numpy as np #define array of values x = np.array([4, 7, 7, 7, 8, 8, 8]) #define values of interest vals = np.array([4, 7, 8]) #find index location of first occurrence of each value of interest sorter = np.argsort(x) sorter[np.searchsorted(x, vals, sorter=sorter)] array([0, 1, 4])

From the output we can see:

- The value
**4**first occurs in index position 0. - The value
**7**first occurs in index position 1. - The value
**8**first occurs in index position 4.

**Additional Resources**

The following tutorials explain how to perform other common operations in NumPy:

How to Map a Function Over a NumPy Array

How to Convert NumPy Array to List in Python

How to Calculate the Magnitude of a Vector Using NumPy