From d2faac63af007e52620c642dfcc576b787b55dcd Mon Sep 17 00:00:00 2001 From: "Miss Islington (bot)" <31488909+miss-islington@users.noreply.github.com> Date: Sun, 17 Nov 2019 22:17:28 -0800 Subject: [PATCH] bpo-38678: Improve argparse example in tutorial (GH-17207) (GH-17213) (cherry picked from commit 04c79d6088a22d467f04dbe438050c26de22fa85) Co-authored-by: Raymond Hettinger --- Doc/library/argparse.rst | 4 +++- Doc/tutorial/stdlib.rst | 32 +++++++++++++++++--------------- 2 files changed, 20 insertions(+), 16 deletions(-) diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst index a2baa077cd890f..4a24c267ec79f4 100644 --- a/Doc/library/argparse.rst +++ b/Doc/library/argparse.rst @@ -778,10 +778,12 @@ how the command-line arguments should be handled. The supplied actions are: example, this is useful for increasing verbosity levels:: >>> parser = argparse.ArgumentParser() - >>> parser.add_argument('--verbose', '-v', action='count') + >>> parser.add_argument('--verbose', '-v', action='count', default=0) >>> parser.parse_args(['-vvv']) Namespace(verbose=3) + Note, the *default* will be ``None`` unless explicitly set to *0*. + * ``'help'`` - This prints a complete help message for all the options in the current parser and then exits. By default a help action is automatically added to the parser. See :class:`ArgumentParser` for details of how the diff --git a/Doc/tutorial/stdlib.rst b/Doc/tutorial/stdlib.rst index 26f11950e79e76..a1b8c23b7bbae0 100644 --- a/Doc/tutorial/stdlib.rst +++ b/Doc/tutorial/stdlib.rst @@ -72,21 +72,23 @@ three`` at the command line:: >>> print(sys.argv) ['demo.py', 'one', 'two', 'three'] -The :mod:`argparse` module provides a mechanism to process command line arguments. -It should always be preferred over directly processing ``sys.argv`` manually. - -Take, for example, the below snippet of code:: - - >>> import argparse - >>> from getpass import getuser - >>> parser = argparse.ArgumentParser(description='An argparse example.') - >>> parser.add_argument('name', nargs='?', default=getuser(), help='The name of someone to greet.') - >>> parser.add_argument('--verbose', '-v', action='count') - >>> args = parser.parse_args() - >>> greeting = ["Hi", "Hello", "Greetings! its very nice to meet you"][args.verbose % 3] - >>> print(f'{greeting}, {args.name}') - >>> if not args.verbose: - >>> print('Try running this again with multiple "-v" flags!') +The :mod:`argparse` module provides a more sophisticated mechanism to process +command line arguments. The following script extracts one or more filenames +and an optional number of lines to be displayed:: + + import argparse + + parser = argparse.ArgumentParser(prog = 'top', + description = 'Show top lines from each file') + parser.add_argument('filenames', nargs='+') + parser.add_argument('-l', '--lines', type=int, default=10) + args = parser.parse_args() + print(args) + +When run at the command line with ``python top.py --lines=5 alpha.txt +beta.txt``, the script sets ``args.lines`` to ``5`` and ``args.filenames`` +to ``['alpha.txt', 'beta.txt']``. + .. _tut-stderr: