How Can I Find the First Index of an Element in a NumPy Array?

Finding the First Index of an Item in a NumPy Array

In Python lists, the index() method allows us to retrieve the first occurrence of an element. Can NumPy provide similar functionality for arrays?

Answer

Yes, NumPy offers a convenient method for locating the first index of an item in an array. You can utilize the np.where function as follows:

import numpy as np

array = np.array([1, 2, 3])
item = 2

itemindex = np.where(array == item)

The np.where function returns a tuple containing the row and column indices where the item is found.

Example

If your array is two-dimensional and contains the item in two locations, then:

array[itemindex[0][0]][itemindex[1][0]]  # equals item
array[itemindex[0][1]][itemindex[1][1]]  # also equals item

This allows you to easily access the desired element based on its first occurrence.

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