NumPy: Test whether all elements in an array evaluate to True

Last update on August 29 2025 12:49:57 (UTC/GMT +8 hours)

Test All Elements are True

Write a NumPy program to test if all elements in an array evaluate to True.
Note: 0 evaluates to False in python.

Pictorial Presentation:

Python NumPy: Test whether all elements in an array evaluate to True

Sample Solution:

Python Code:

# Importing the NumPy library with an alias 'np'
import numpy as np

# Checking if all elements along a specified axis evaluate to True or non-zero
print(np.all([[True,False],[True,True]]))  # Evaluates to False because at least one element in the array is False
print(np.all([[True,True],[True,True]]))   # Evaluates to True because all elements in the array are True

# Checking if all elements in an iterable evaluate to True or non-zero
print(np.all([10, 20, 0, -50]))   # Evaluates to False because 0 (which evaluates to False) is present in the list
print(np.all([10, 20, -50]))      # Evaluates to True because all elements in the list are non-zero and evaluate to True

Sample Output:

Explanation:

In the above code –

print(np.all([[True,False],[True,True]])): np.all checks if all elements of the input array are True. In this case, there is a False value in the array, so the output is False.

print(np.all([[True,True],[True,True]])): np.all checks if all elements of the input array are True. In this case, all elements are True, so the output is True.

print(np.all([10, 20, 0, -50])): np.all checks if all elements of the input array are non-zero. In this case, there is a zero in the array, so the output is False.

print(np.all([10, 20, -50])): np.all checks if all elements of the input array are non-zero. In this case, all elements are non-zero, so the output is True.

For more Practice: Solve these Related Problems:

Use np.all to check if every element in a boolean array evaluates to True.
Convert a numeric array to boolean and test if all elements are nonzero.
Create a function that tests the truth value of an array along a specific axis.
Verify the all condition on an array containing mixed true (nonzero) and false (zero) values.

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