How to Check if a NumPy Array is Empty

To check if a NumPy array is empty, use the array.size attribute. If array.size equals 0, the array has no elements and is empty.

Syntax

Use the size attribute of a NumPy array to find the total number of elements it contains.

• array.size: Returns the number of elements in the array.
• If array.size == 0, the array is empty.

python

import numpy as np

array = np.array([])

if array.size == 0:
    print("Array is empty")
else:
    print("Array is not empty")

Output

Array is empty

Example

This example shows how to create an empty and a non-empty NumPy array, then check if each is empty using the size attribute.

python

import numpy as np

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

print(f"empty_array.size = {empty_array.size}")
print(f"non_empty_array.size = {non_empty_array.size}")

if empty_array.size == 0:
    print("empty_array is empty")
else:
    print("empty_array is not empty")

if non_empty_array.size == 0:
    print("non_empty_array is empty")
else:
    print("non_empty_array is not empty")

Output

empty_array.size = 0
non_empty_array.size = 3
empty_array is empty
non_empty_array is not empty

Common Pitfalls

A common mistake is to check if the array itself is None or use if array: which does not work for NumPy arrays and raises an error. Always use array.size == 0 to check emptiness.

python

import numpy as np

array = np.array([])

# Wrong way - raises ValueError
# if array:
#     print("Array is not empty")

# Correct way
if array.size == 0:
    print("Array is empty")
else:
    print("Array is not empty")

Output

Array is empty

Quick Reference

Check	Code	Meaning
Is array empty?	array.size == 0	True if no elements in array
Is array not empty?	array.size > 0	True if array has elements

Key Takeaways

Use array.size to check the number of elements in a NumPy array.

An array is empty if array.size == 0.

Do not use if array: to check emptiness; it raises an error.

Checking array is None does not tell if the array is empty.

This method works for arrays of any shape or dimension.