5.2 Comparing arrays

Comparing two arrays is not as simple as it may seem. Consider the following code, which is intended to check whether two matrices are close to each other:

A = array([0.,0.])
B = array([0.,0.])
if abs(B-A) < 1e-10: # an exception is raised here
    print("The two arrays are close enough")

This code raises the following exception when the if statement is executed:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

In this section, we'll explain why this is so and how to remedy this state of affairs.