- Issue #15935: Clarification of argparse docs, re: add_argument() type and
default arguments. Patch contributed by Chris Jerdonek.
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index 1313e4b..5273e9b 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -904,6 +904,17 @@
>>> parser.parse_args(''.split())
Namespace(foo=42)
+If the ``default`` value is a string, the parser parses the value as if it
+were a command-line argument. In particular, the parser applies any type_
+conversion argument, if provided, before setting the attribute on the
+:class:`Namespace` return value. Otherwise, the parser uses the value as is::
+
+ >>> parser = argparse.ArgumentParser()
+ >>> parser.add_argument('--length', default='10', type=int)
+ >>> parser.add_argument('--width', default=10.5, type=int)
+ >>> parser.parse_args()
+ Namespace(length=10, width=10.5)
+
For positional arguments with nargs_ equal to ``?`` or ``*``, the ``default`` value
is used when no command-line argument was present::
@@ -942,6 +953,9 @@
>>> parser.parse_args('2 temp.txt'.split())
Namespace(bar=<_io.TextIOWrapper name='temp.txt' encoding='UTF-8'>, foo=2)
+See the section on the default_ keyword argument for information on when the
+``type`` argument is applied to default arguments.
+
To ease the use of various types of files, the argparse module provides the
factory FileType which takes the ``mode=`` and ``bufsize=`` arguments of the
:func:`open` function. For example, ``FileType('w')`` can be used to create a
diff --git a/Misc/NEWS b/Misc/NEWS
index ab3c7d4..2285f8c 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -589,6 +589,9 @@
Documentation
-------------
+- Issue #15935: Clarification of argparse docs, re: add_argument() type and
+ default arguments. Patch contributed by Chris Jerdonek.
+
- Issue #11964: Document a change in v3.2 to the behavior of the indent
parameter of json encoding operations.