- 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 8bb740e..2380a50 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -906,6 +906,17 @@
>>> 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::
@@ -944,6 +955,9 @@
>>> parser.parse_args('2 temp.txt'.split())
Namespace(bar=<open file 'temp.txt', mode 'r' at 0x...>, 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
``file`` object. For example, ``FileType('w')`` can be used to create a