In Python, what is the difference between a list and a tuple?

• A. Lists are immutable; tuples are mutable.
• B. Tuples are mutable.
• C. Lists are mutable; tuples are immutable.
• D. Lists are immutable; tuples are immutable.

Answer: (C)

Mutability is the main idea here. A list in Python is mutable, meaning you can change its contents after it’s created. You can replace items by index, add items with append or extend, or remove items with pop or remove, all on the same object. A tuple, by contrast, is immutable: once it’s created, you can’t change its elements or its size. If you try to modify a tuple, Python raises a TypeError. If you need a different collection, you typically create a new tuple from parts, for example by concatenation, or convert to a list, modify it, then convert back.

Because of this immutability, tuples can be used as dictionary keys or set elements (assuming their contents are hashable), whereas lists cannot be used in those roles. So the correct idea is that lists are mutable and tuples are immutable.