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Diffstat (limited to 'Doc/library/argparse.rst')
| -rw-r--r-- | Doc/library/argparse.rst | 23 |
1 files changed, 20 insertions, 3 deletions
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst index 4203e8b..9f6a1ea 100644 --- a/Doc/library/argparse.rst +++ b/Doc/library/argparse.rst @@ -130,9 +130,12 @@ command-line arguments from :data:`sys.argv`. ArgumentParser objects ---------------------- -.. class:: ArgumentParser([description], [epilog], [prog], [usage], [add_help], \ - [argument_default], [parents], [prefix_chars], \ - [conflict_handler], [formatter_class]) +.. class:: ArgumentParser(prog=None, usage=None, description=None, \ + epilog=None, parents=[], \ + formatter_class=argparse.HelpFormatter, \ + prefix_chars='-', fromfile_prefix_chars=None, \ + argument_default=None, conflict_handler='error', \ + add_help=True) Create a new :class:`ArgumentParser` object. Each parameter has its own more detailed description below, but in short they are: @@ -920,6 +923,17 @@ was not present at the command line:: >>> 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:: @@ -958,6 +972,9 @@ types and functions can be used directly as the value of the ``type`` argument:: >>> 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 |