bpo-28638: Optimize namedtuple() creation time by minimizing use of exec() (#3454)

* Working draft without _source

* Re-use itemgetter() instances

* Speed-up calls to __new__() with a pre-bound tuple.__new__()

* Add note regarding string interning

* Remove unnecessary create function wrappers

* Minor sync-ups with PR-2736.  Mostly formatting and f-strings

* Bring-in qualname/__module fix-ups from PR-2736

* Formally remove the verbose flag and _source attribute

* Restore a test of potentially problematic field names

* Restore kwonly_args test but without the verbose option

* Adopt Inada's idea to reuse the docstrings for the itemgetters

* Neaten-up a bit

* Add news blurb

* Serhiy pointed-out the need for interning

* Jelle noticed as missing f on an f-string

* Add whatsnew entry for feature removal

* Accede to request for dict literals instead keyword arguments

* Leave the method.__module__ attribute pointing the actual location of the code

* Improve variable names and add a micro-optimization for an non-public helper function

* Simplify by in-lining reuse_itemgetter()

* Arrange steps in more logical order

* Save docstring in local cache instead of interning

1 files changed, 4 insertions, 14 deletions

diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index d6d2056..cda8296 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -763,7 +763,7 @@ Named tuples assign meaning to each position in a tuple and allow for more reada
 self-documenting code.  They can be used wherever regular tuples are used, and
 they add the ability to access fields by name instead of position index.
 
-.. function:: namedtuple(typename, field_names, *, verbose=False, rename=False, module=None)
+.. function:: namedtuple(typename, field_names, *, rename=False, module=None)
 
     Returns a new tuple subclass named *typename*.  The new subclass is used to
     create tuple-like objects that have fields accessible by attribute lookup as
@@ -786,10 +786,6 @@ they add the ability to access fields by name instead of position index.
     converted to ``['abc', '_1', 'ghi', '_3']``, eliminating the keyword
     ``def`` and the duplicate fieldname ``abc``.
 
-    If *verbose* is true, the class definition is printed after it is
-    built.  This option is outdated; instead, it is simpler to print the
-    :attr:`_source` attribute.
-
     If *module* is defined, the ``__module__`` attribute of the named tuple is
     set to that value.
 
@@ -806,6 +802,9 @@ they add the ability to access fields by name instead of position index.
     .. versionchanged:: 3.6
        Added the *module* parameter.
 
+    .. versionchanged:: 3.7
+       Remove the *verbose* parameter and the :attr:`_source` attribute.
+
 .. doctest::
     :options: +NORMALIZE_WHITESPACE
 
@@ -878,15 +877,6 @@ field names, the method and attribute names start with an underscore.
         >>> for partnum, record in inventory.items():
         ...     inventory[partnum] = record._replace(price=newprices[partnum], timestamp=time.now())
 
-.. attribute:: somenamedtuple._source
-
-    A string with the pure Python source code used to create the named
-    tuple class.  The source makes the named tuple self-documenting.
-    It can be printed, executed using :func:`exec`, or saved to a file
-    and imported.
-
-    .. versionadded:: 3.3
-
 .. attribute:: somenamedtuple._fields
 
     Tuple of strings listing the field names.  Useful for introspection