When Do Python's `is` and `==` Operators Produce Different Results?

Understanding the "is" Operator Revisited

The "is" operator in programming languages such as Python is a powerful tool that enables comparison of objects beyond their values. Contrary to common misconceptions, "is" does not compare the values of variables, but rather the instances themselves. To understand this distinction, consider the example provided:

x = [1, 2, 3]
y = [1, 2, 3]

print(x is y)  # False

Here, the "is" operator returns False, indicating that the variables x and y refer to distinct instances, despite having identical values. This difference stems from the concept of object identity in Python.

Each object in Python, including lists, is stored as a unique instance with its own memory location. The "id()" function can be used to retrieve the memory address of an object, revealing that x and y have separate addresses:

print(id(x))  # 123456789
print(id(y))  # 987654321

When using the "is" operator, it checks if two variables refer to the exact same instance. In this case, x and y are separate instances of the list type, even though their contents are identical.

To compare values instead of object identity, the "==" equality operator should be used:

print(x == y)  # True

In contrast to "is," "==" verifies if the values of two objects match.

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