Lists and tuples

Two of the most basic collection types in Python are lists and tuples, and they both represent sequences of objects. The basic difference between them should be obvious for anyone who has spent more than a few hours with Python; lists are dynamic, so they can change their size, while tuples are immutable (cannot be modified after they are created).

Lists and tuples in Python have various optimizations that make allocations/deallocations of small objects fast. They are also the recommended datatypes for structures where the position of the element is information by itself. For example, a tuple may be a good choice for storing a pair of (x, y) coordinates. Implementation details regarding tuples are not interesting. The only important thing about them in the scope of this chapter is that tuple is immutable and thus hashable. A detailed explanation of this section will be covered later in the Dictionaries section. More interesting than tuples is its dynamic counterpart – lists. In the next section, we will discuss how it really works, and how to deal with it efficiently.