bpo-38678: Improve argparse example in tutorial (GH-17207)
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index 9a1cf3a..f8e3918 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -810,10 +810,12 @@
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 f32063e..a52653b 100644
--- a/Doc/tutorial/stdlib.rst
+++ b/Doc/tutorial/stdlib.rst
@@ -72,21 +72,23 @@
>>> 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.
+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::
-Take, for example, the below snippet of code::
+ import argparse
- >>> 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!')
+ 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: