#14840: Add a bit on the difference between tuples and lists. Initial patch by Zachary Ware.

1 files changed, 21 insertions, 9 deletions

diff --git a/Doc/tutorial/datastructures.rst b/Doc/tutorial/datastructures.rst
index 5fb72fd..eec34f0 100644
--- a/Doc/tutorial/datastructures.rst
+++ b/Doc/tutorial/datastructures.rst
@@ -349,17 +349,31 @@ A tuple consists of a number of values separated by commas, for instance::
    ... u = t, (1, 2, 3, 4, 5)
    >>> u
    ((12345, 54321, 'hello!'), (1, 2, 3, 4, 5))
+   >>> # Tuples are immutable:
+   ... t[0] = 88888
+   Traceback (most recent call last):
+     File "<stdin>", line 1, in <module>
+   TypeError: 'tuple' object does not support item assignment
+   >>> # but they can contain mutable objects:
+   ... v = ([1, 2, 3], [3, 2, 1])
+   >>> v
+   ([1, 2, 3], [3, 2, 1])
+
 
 As you see, on output tuples are always enclosed in parentheses, so that nested
 tuples are interpreted correctly; they may be input with or without surrounding
 parentheses, although often parentheses are necessary anyway (if the tuple is
-part of a larger expression).
-
-Tuples have many uses.  For example: (x, y) coordinate pairs, employee records
-from a database, etc.  Tuples, like strings, are immutable: it is not possible
-to assign to the individual items of a tuple (you can simulate much of the same
-effect with slicing and concatenation, though).  It is also possible to create
-tuples which contain mutable objects, such as lists.
+part of a larger expression).  It is not possible to assign to the individual
+items of a tuple, however it is possible to create tuples which contain mutable
+objects, such as lists.
+
+Though tuples may seem similar to lists, they are often used in different
+situations and for different purposes.
+Tuples are :term:`immutable`, and usually contain an heterogeneous sequence of
+elements that are accessed via unpacking (see later in this section) or indexing
+(or even by attribute in the case of :func:`namedtuples <collections.namedtuple>`).
+Lists are :term:`mutable`, and their elements are usually homogeneous and are
+accessed by iterating over the list.
 
 A special problem is the construction of tuples containing 0 or 1 items: the
 syntax has some extra quirks to accommodate these.  Empty tuples are constructed
@@ -388,8 +402,6 @@ many variables on the left side of the equals sign as there are elements in the
 sequence.  Note that multiple assignment is really just a combination of tuple
 packing and sequence unpacking.
 
-.. XXX Add a bit on the difference between tuples and lists.
-
 
 .. _tut-sets: