What is numpy.isneginf() in Python?

Python’s numpy.isneginf() is used to test if an element is negative infinity or not. It tests an array element-wise and returns a boolean array as the output.

Syntax

numpy.isneginf is declared as follows:

numpy.isneginf(x, out=None)

In the syntax above, x is the non-optional parameter, and out is the optional parameter.

Parameters

The numpy.isneginf() method takes the following compulsory parameter:

  • x [array-like] - input array.

The numpy.isneginf() method takes the following optional parameter:

  • out [array_like, optional] - represents the location into which the output of the method is stored. If out is not specified or is None, a freshly-allocated boolean array is returned.

Return value

numpy.isneginf returns a boolean array with the same dimensions as x. The method returns True /False or 0/1 depending on the following factors:

  • If out is not specified, a boolean array is returned. If the element is negative infinity, True is returned. Otherwise, False is returned.

  • If out is specified and the type is a numerical array, the result is a numerical array. The integer value 1 is returned if the element is negative infinity; otherwise, the method returns 0.

An error occurs in the case of the following:

  • If x is scalar and out is specified.

  • If x and out have different shapes.

  • If x contains complex values.

Examples

The example below shows the use of numpy.isneginf() on the elements a and b:

import numpy as np
a = -np.inf
b = np.inf
print (np.isneginf(a))
print (np.isneginf(b))

The following example shows the use of numpy.isneginf() on the array arr1 when out is not specified:

import numpy as np
arr1 = np.array([2, -np.inf, 0, np.nan])
print (np.isneginf(arr1))

The following example shows the use of numpy.isneginf() on the array arr2 when out is specified:

import numpy as np
arr2 = np.array([-np.inf, 2, 0])
out = np.array([1,1,1])
print (np.isneginf(arr2,out))

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