[Python-checkins] cpython (2.7): - Issue #15935: Clarification of argparse docs, re: add_argument() type and
barry.warsaw
python-checkins at python.org
Tue Sep 25 16:48:34 CEST 2012
http://hg.python.org/cpython/rev/b624059a8dac
changeset: 79165:b624059a8dac
branch: 2.7
parent: 79159:8a22a2804a66
user: Barry Warsaw <barry at python.org>
date: Tue Sep 25 10:32:53 2012 -0400
summary:
- Issue #15935: Clarification of argparse docs, re: add_argument() type and
default arguments. Patch contributed by Chris Jerdonek.
files:
Doc/library/argparse.rst | 14 ++++++++++++++
Misc/NEWS | 3 +++
2 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
--- 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
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -442,6 +442,9 @@
Documentation
-------------
+- Issue #15935: Clarification of argparse docs, re: add_argument() type and
+ default arguments. Patch contributed by Chris Jerdonek.
+
- Issue #13769: Document the effect of ensure_ascii to the return type
of JSON decoding functions.
--
Repository URL: http://hg.python.org/cpython
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