NumPy argwhere()

argwhere() Syntax

The syntax of argwhere() is:

numpy.argwhere(array)

argwhere() Argument

The argwhere() method takes one argument:

• array - an array whose non-zero indices are to be found

argwhere() Return Value

The argwhere() method returns indices of elements that are non-zero as a 2D array.

Example 1: numpy.argwhere() With Arrays

Output

Array of non-empty indices in numberArray:
[[0]
 [3]
 [4]]

Array of non-empty indices in  stringArray:
 [[0]
 [1]
 [3]]

Example 2: numpy.argwhere() With 2-D Arrays

Output

[[0 0]
 [0 2]
 [1 0]
 [2 1]
 [2 2]] 

Here, the output represents the positions of non-zero elements in the row-column format.

The first non-zero element is 1, which is in index [0, 0] in row-column format. Similarly, the second non-zero element is 3, which is in index [0, 2] in row-column format, and so on.

Example 3: numpy.argwhere() With Condition

We can also use argwhere() to find the indices of elements that satisfy the given condition.

Output

[[1]
 [3]
 [5]]

Note: To group the indices by the dimension, rather than element, we use nonzero().