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Numpy – Check If a Number is Complex

In this tutorial, we will look at how to check if a number in a Numpy array is complex or not with the help of some examples. Complex numbers in mathematics are numbers that have an imaginary part, for example, 1 + 2j.

How to test for a complex number in a Numpy array?

check if a number is complex or not in numpy array

You can use the numpy.iscomplex() function to check (element-wise) if values in a Numpy array are complex or not. The following is the syntax –

# test for complex numbers - pass scaler value or numpy array
np.iscomplex(a)

The numpy.iscomplex() function essentially tests (element-wise) whether the number has a non-zero imaginary part or not. It returns a boolean array if you pass an array and if you pass a scaler value, it returns a boolean value.

Examples

Let’s now look at some examples of using the above function to test for complex numbers.

Example 1 – Check if a number is complex or not using numpy.iscomplex()

First, let’s pass scaler values to the numpy.iscomplex() function.

Let’s apply the numpy.iscomplex() function on three scaler values – a real number, a complex number with a non-zero imaginary part, and a complex number with the imaginary part as 0.

import numpy as np

# check if complex
print(np.iscomplex(14))
print(np.iscomplex(2 + 4j))
print(np.iscomplex(2 + 0j))

Output:

False
True
False

We get False as the output for the real number 14 and the complex number having 0 as its imaginary part. And we get True as the output for the complex number with a non-zero imaginary part.

Note that here, even though the value 2 + 0j is of complex type, the numpy.iscomplex() function returns it as not a complex value (since its imaginary part is 0 which essentially makes it a real value).

If, on the other hand, you want to check whether the value is of complex type, use the numpy.iscomplexobj() function.

# check if complex type object
print(np.iscomplexobj(14))
print(np.iscomplexobj(2 + 4j))
print(np.iscomplexobj(2 + 0j))

Output:

False
True
True

We get False as the output for the real number 14 and True as the output for both the complex type values (irrespective of whether the imaginary part is 0 or not).

Example 2 – Element-wise check for complex number in a Numpy array using numpy.iscomplex()

If you apply the numpy.iscomplex() function on an array, it will return a boolean array containing True for the values that are complex and False for the other values.

Let’s create a 1-D array and apply the numpy.iscomplex() function to it.

# create a numpy array
ar = np.array([1, 2+3j, 2+0j, 4, 5.7, np.nan, np.inf, 1j, 0+0j])
# element-wise check for complex value in ar
np.iscomplex(ar)

Output:

array([False,  True, False, False, False, False, False,  True, False])

We get a boolean array as an output. You can see that in the boolean array we get True for only the values that test as a complex number in the original array.

Summary

In this tutorial, we looked at how we can use the numpy.iscomplex() function to check if a number is complex or not in a Numpy array. Keep in mind that this function checks whether the imaginary part of the number is non-zero or not. If you want to check whether the number is of complex type, use the numpy.iscomplexobj() function instead.

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Author

  • Piyush

    Piyush is a data scientist passionate about using data to understand things better and make informed decisions. In the past, he's worked as a Data Scientist for ZS and holds an engineering degree from IIT Roorkee. His hobbies include watching cricket, reading, and working on side projects.