The tuple object (pronounced “toople” or “tuhple,” depending on whom you ask) is roughly like a list that cannot be changed—tuples are sequences, like lists, but they are immutable, like strings. Functionally, they’re used to represent fixed collections of items: the components of a specific calendar date, for instance. Syntactically, they are normally 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 type-specific callable methods as of Python 2.6 and 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 (one-item tuples like the one here require a trailing comma):

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

>>> T = (2,) + T[1:]            # Make a new tuple for a new value
>>> T
(2, 2, 3, 4)

Like lists and dictionaries, tuples support mixed types and nesting, but they don’t grow and shrink because they are immutable (the parentheses enclosing a tuple’s items can usually be omitted, as done here):

>>> 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'