Tuples

The tuple object (pronounced “toople” or “tuhple,” depending on who you ask) is roughly like a list that cannot be changed—tuples are sequences, like lists, but they are immutable, like strings. Syntactically, they are coded in parentheses instead of square brackets, and they support arbitrary types, arbitrary nesting, and the usual sequence operations:

>>> T = (1, 2, 3, 4)            # A 4-item tuple
>>> len(T)                      # Length
4

>> T + (5, 6)                   # Concatenation
(1, 2, 3, 4, 5, 6)

>>> T[0]                        # Indexing, slicing, and more
1

Tuples also have two type-specific callable methods in Python 3.0, but not nearly as many as lists:

>>> T.index(4)                  # Tuple methods: 4 appears at offset 3
3
>>> T.count(4)                  # 4 appears once
1

The primary distinction for tuples is that they cannot be changed once created. That is, they are immutable sequences:

>>> T[0] = 2                    # Tuples are immutable
...error text omitted...
TypeError: 'tuple' object does not support item assignment

Like lists and dictionaries, tuples support mixed types and nesting, but they don’t grow and shrink because they are immutable:

>>> T = ('spam', 3.0, [11, 22, 33])
>>> T[1]
3.0
>>> T[2][1]
22
>>> T.append(4)
AttributeError: 'tuple' object has no attribute 'append'