bpo-38096: Clean up the "struct sequence" / "named tuple" docs (GH-15895)

* bpo-38096: Clean up the "struct sequence" / "named tuple" docs

* Fix remaining occurrences of "struct sequence"

* Repair a user visible docstring

1 files changed, 22 insertions, 19 deletions

diff --git a/Doc/glossary.rst b/Doc/glossary.rst
index 0f2a3a1..84d0fca 100644
--- a/Doc/glossary.rst
+++ b/Doc/glossary.rst
@@ -739,17 +739,28 @@ Glossary
       also :term:`immutable`.
 
    named tuple
-      Any tuple-like class whose indexable elements are also accessible using
-      named attributes (for example, :func:`time.localtime` returns a
-      tuple-like object where the *year* is accessible either with an
-      index such as ``t[0]`` or with a named attribute like ``t.tm_year``).
-
-      A named tuple can be a built-in type such as :class:`time.struct_time`,
-      or it can be created with a regular class definition.  A full featured
-      named tuple can also be created with the factory function
-      :func:`collections.namedtuple`.  The latter approach automatically
-      provides extra features such as a self-documenting representation like
-      ``Employee(name='jones', title='programmer')``.
+      The term "named tuple" applies to any type or class that inherits from
+      tuple and whose indexable elements are also accessible using named
+      attributes.  The type or class may have other features as well.
+
+      Several built-in types are named tuples, including the values returned
+      by :func:`time.localtime` and :func:`os.stat`.  Another example is
+      :data:`sys.float_info`::
+
+           >>> sys.float_info[1]                   # indexed access
+           1024
+           >>> sys.float_info.max_exp              # named field access
+           1024
+           >>> isinstance(sys.float_info, tuple)   # kind of tuple
+           True
+
+      Some named tuples are built-in types (such as the above examples).
+      Alternatively, a named tuple can be created from a regular class
+      definition that inherits from :class:`tuple` and that defines named
+      fields.  Such as class can be written by hand or it can be created with
+      the factory function :func:`collections.namedtuple`.  The latter
+      technique also adds some extra methods that may not be found in
+      hand-written or built-in named tuples.
 
    namespace
       The place where a variable is stored.  Namespaces are implemented as
@@ -1032,14 +1043,6 @@ Glossary
       an :term:`expression` or one of several constructs with a keyword, such
       as :keyword:`if`, :keyword:`while` or :keyword:`for`.
 
-   struct sequence
-      A tuple with named elements. Struct sequences expose an interface similar
-      to :term:`named tuple` in that elements can be accessed either by
-      index or as an attribute. However, they do not have any of the named tuple
-      methods like :meth:`~collections.somenamedtuple._make` or
-      :meth:`~collections.somenamedtuple._asdict`. Examples of struct sequences
-      include :data:`sys.float_info` and the return value of :func:`os.stat`.
-
    text encoding
       A codec which encodes Unicode strings to bytes.