Learning Python

Tuples

The last collection type in our survey is the Python tuple. Tuples construct simple groups of objects. They work exactly like lists, except that tuples can’t be changed in place (they’re immutable) and are usually written as a series of items in parentheses, not square brackets. Tuples share most of their properties with lists. They are:

Ordered collections of arbitrary objects

Like strings and lists, tuples are an ordered collection of objects; like lists, they can embed any kind of object.

Accessed by offset

Like strings and lists, items in a tuple are accessed by offset (not key); they support all the offset-base access operations we’ve already seen, such as indexing and slicing.

Of the category immutable sequence

Like strings, tuples are immutable; they don’t support any of the in-place change operations we saw applied to lists. Like strings and lists, tuples are sequences; they support many of the same operations.

Fixed length, heterogeneous, arbitrarily nestable

Because tuples are immutable, they can’t grow or shrink without making a new tuple; on the other hand, tuples can hold other compound objects (e.g., lists, dictionaries, other tuples) and so support nesting.

Arrays of object references

Like lists, tuples are best thought of as object reference arrays; tuples store access points to other objects (references), and indexing a tuple is relatively quick.

Table 2.9 highlights common tuple operations. Tuples are written as a series of objects (really, expressions), separated ...