What is the key difference between '==' and 'is' in Python?

In Python, the '==' operator is used to check for value equality, meaning it evaluates whether the values of two objects are the same, regardless of whether they are the same object in memory. For example, two different lists containing the same elements will return True when compared with '==' because their values are equal.

On the other hand, the 'is' operator checks for object identity, meaning it evaluates whether two references point to the same object in memory. If two variables are assigned to the same object, using 'is' between them will return True.

Understanding this distinction is crucial for programming in Python, especially when dealing with mutable and immutable types, as it can lead to different behaviors when comparing objects. For instance, immutable types, like integers and strings, can sometimes appear to behave similarly with '==' and 'is' due to Python's optimization techniques like interning, but this is not a reliable rule.

Recognizing what '==' and 'is' are designed for enables you to write clearer and more effective Python code, ensuring you are checking value equality or object identity as needed in your applications.