[issue14034] Add argparse howto
Tshepang Lekhonkhobe
report at bugs.python.org
Mon Mar 19 15:48:34 CET 2012
Tshepang Lekhonkhobe <tshepang at gmail.com> added the comment:
Fixing a markup error. Sorry for the noise.
----------
Added file: http://bugs.python.org/file24942/argparse_howto3.patch
_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue14034>
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diff --git a/Doc/howto/argparse.rst b/Doc/howto/argparse.rst
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+++ b/Doc/howto/argparse.rst
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+*****************************
+Command Line Interface HOWTO
+*****************************
+
+:author: Tshepang Lekhonkhobe <tshepang at gmail.com>
+
+.. _argparse-howto:
+
+This is intended to be a gentle introduction to command line parsing
+using :mod:`argparse` module, the recommended module for such a purpose
+in Python. Please pay careful attention to the code and its output. All of
+it was carefully selected for its instructive value.
+
+.. note::
+
+ There's two other modules that fulfill the same task, namely
+ :mod:`getopt` (an equivalent for :c:func:`getopt` from the C
+ language) and the deprecated :mod:`optparse`.
+
+
+Concepts
+========
+
+Let's show the sort of functionality that we are going to explore in this
+introductory tutorial by making use of the :command:`ls` command::
+
+
+ $ ls
+ cpython devguide prog.py pypy rm-unused-function.patch
+ $ ls pypy
+ ctypes_configure demo dotviewer include lib_pypy lib-python ...
+ $ ls -l
+ total 20
+ drwxr-xr-x 19 wena wena 4096 Feb 18 18:51 cpython
+ drwxr-xr-x 4 wena wena 4096 Feb 8 12:04 devguide
+ -rwxr-xr-x 1 wena wena 535 Feb 19 00:05 prog.py
+ drwxr-xr-x 14 wena wena 4096 Feb 7 00:59 pypy
+ -rw-r--r-- 1 wena wena 741 Feb 18 01:01 rm-unused-function.patch
+ $ ls --help
+ Usage: ls [OPTION]... [FILE]...
+ List information about the FILEs (the current directory by default).
+ Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.
+ ...
+
+A few concepts we can learn from the four commands:
+
+#. The :command:`ls` command is useful when run without any options at all. It defaults
+ to displaying the contents of the current directory.
+
+#. If we want beyond what it provides by default, we tell it a bit more. In
+ this case, we want it to display a different directory, ``pypy``.
+ What we did is specify what is known as a positional argument. It's named so
+ because the program should know what to do with the value, solely based on
+ where it appears on the command line. This concept is more relevant
+ to a command like :command:`cp`, whose most basic usage is ``cp SRC DEST``.
+ The first position is *what you want copied,* and the second
+ position is *where you want it copied to*.
+
+#. Now, say we want to change behaviour of the program. In our example,
+ we display more info for each file instead of just showing the file names.
+ The ``-l`` in that case is known as an optional argument.
+
+#. That's a snippet of the help text. It's very useful in that you can
+ come across a program you have never used before, and can figure out
+ how it works simply by reading it's help text.
+
+
+The basics
+==========
+
+Let us start with a very simple example which does (almost) nothing::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.parse_args()
+
+Following is a result of running the code::
+
+ $ python3 prog.py
+ $ python3 prog.py --help
+ usage: prog.py [-h]
+
+ optional arguments:
+ -h, --help show this help message and exit
+ $ python3 prog.py --verbose
+ usage: prog.py [-h]
+ prog.py: error: unrecognized arguments: --verbose
+ $ python3 prog.py foo
+ usage: prog.py [-h]
+ prog.py: error: unrecognized arguments: foo
+
+Here is what is happening:
+
+* Running the script without any options results in nothing displayed to
+ stdout. Not so useful.
+
+* The second one starts to display the usefulness of the :mod:`argparse`
+ module. We have done almost nothing, but already we get a nice help message.
+
+* The ``--help`` option, which can also be shortened to ``-h``, is the only
+ option we get for free (i.e. no need to specify it). Specifying anything
+ else results in an error. But even then, we do get a useful usage message,
+ also for free.
+
+
+Introducing Positional arguments
+================================
+
+An example::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("echo")
+ args = parser.parse_args()
+ print(args.echo)
+
+And running the code::
+
+ $ python3 prog.py
+ usage: prog.py [-h] echo
+ prog.py: error: the following arguments are required: echo
+ $ python3 prog.py --help
+ usage: prog.py [-h] echo
+
+ positional arguments:
+ echo
+
+ optional arguments:
+ -h, --help show this help message and exit
+ $ python3 prog.py foo
+ foo
+
+Here is what's happening:
+
+#. We've added :meth:`add_argument` method, which is what we use to specify
+ which command line options the program is willing to accept. In this case,
+ I've named it ``echo`` so that it's in line with its function.
+
+#. Calling our program now requires us to specify an option.
+
+#. Also, the :meth:`parse_args` method actually returns some data from the
+ options specified, in this case, ``echo``. Note that the variable is some
+ form of 'magic' that :mod:`argparse` performs for free (i.e. no need to
+ specify which variable that value is stored in). Note also that it's
+ name matches the string argument given to the method, ``echo``.
+
+Note however that, although the help display looks nice and all, it currently
+is not as helpful as it can be. For example we see that we got ``echo`` as a
+positional argument, but we don't know what it does, other than by guessing or
+by reading the source code. So, let's make it a bit more useful::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("echo", help="echo the string you use here")
+ args = parser.parse_args()
+ print(args.echo)
+
+And we get::
+
+ $ python3 prog.py -h
+ usage: prog.py [-h] echo
+
+ positional arguments:
+ echo echo the string you use here
+
+ optional arguments:
+ -h, --help show this help message and exit
+
+Now, how about doing something even more useful::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", help="display a square of a given number")
+ args = parser.parse_args()
+ print(pow(args.square, 2))
+
+Following is a result of running the code::
+
+ $ python3 prog.py 4
+ Traceback (most recent call last):
+ File "prog.py", line 5, in <module>
+ print(pow(args.square, 2))
+ TypeError: unsupported operand type(s) for ** or pow(): 'str' and 'int'
+
+That didn't go so well. That's because :mod:`argparse` treats the options we
+give it as strings, unless we tell it otherwise and the :func:`pow` function
+doesn't accept strings as arguments. So, let's tell
+:mod:`argparse` to treat that input as an integer::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", help="display a square of a given number",
+ type=int)
+ args = parser.parse_args()
+ print(pow(args.square, 2))
+
+Following is a result of running the code::
+
+ $ python3 prog.py 4
+ 16
+ $ python3 prog.py four
+ usage: prog.py [-h] square
+ prog.py: error: argument square: invalid int value: 'four'
+
+That went well. The program now even helpfully quits on bad illegal input
+before proceeding.
+
+
+Introducing Optional arguments
+==============================
+
+So far we, have been playing with positional arguments. Let us
+have a look on how to add optional ones::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("--verbosity", help="increase output verbosity")
+ args = parser.parse_args()
+ if args.verbosity:
+ print("verbosity turned on")
+
+And the output::
+
+ $ python3 prog.py --verbosity 1
+ verbosity turned on
+ $ python3 prog.py
+ $ python3 prog.py --help
+ usage: prog.py [-h] [--verbosity VERBOSITY]
+
+ optional arguments:
+ -h, --help show this help message and exit
+ --verbosity VERBOSITY
+ increase output verbosity
+ $ python3 prog.py --verbosity
+ usage: prog.py [-h] [--verbosity VERBOSITY]
+ prog.py: error: argument --verbosity: expected one argument
+
+Here is what is happening:
+
+#. The program is written so as to display something when ``--verbosity`` is
+ specified and display nothing when not.
+
+#. To show that the option is actually optional, there is no error when running
+ the program without it. Note that by default, if an optional argument isn't
+ used, the relevant variable, in this case :data:`args.verbosity`, is
+ given ``None`` as a value, which is the reason it fails the truth
+ test of the :keyword:`if` statement.
+
+#. The help message is a bit different.
+
+#. When using the ``--verbosity`` option, one must also specify some value, any
+ value.
+
+The above example accepts arbitrary integer values for ``--verbosity``, but for
+our simple program, only two values are actually useful, ``True`` or ``False``.
+Let's modify the code accordingly::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("--verbose", help="increase output verbosity",
+ action="store_true")
+ args = parser.parse_args()
+ if args.verbose:
+ print("verbosity turned on")
+
+And the output::
+
+ $ python3 prog.py --verbose
+ verbosity turned on
+ $ python3 prog.py --verbose 1
+ usage: prog.py [-h] [--verbose]
+ prog.py: error: unrecognized arguments: 1
+ $ python3 prog.py --help
+ usage: prog.py [-h] [--verbose]
+
+ optional arguments:
+ -h, --help show this help message and exit
+ --verbose increase output verbosity
+
+Here is what is happening:
+
+#. The option is now more of a flag than something that requires a value.
+ We even changed the name of the option to match that idea.
+ Note that we now specify a new keyword, ``action``, and give it the value
+ "store_true". This means that, if the option is specified, assign the value
+ ``True`` to :data:`args.verbose` ``True``. Not specifying it implies
+ ``False``.
+
+#. It complains when you specify a value, in true spirit of what flags
+ actually are.
+
+#. Notice the different help text.
+
+If you are familiar with command line usage, you will notice that I haven't yet
+touched on the topic of short versions of the options. It's quite simple::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("-v", "--verbose", help="increase output verbosity",
+ action="store_true")
+ args = parser.parse_args()
+ if args.verbose:
+ print("verbosity turned on")
+
+And here goes::
+
+ $ python3 prog.py -v
+ verbosity turned on
+ $ python3 prog.py --help
+ usage: prog.py [-h] [-v]
+
+ optional arguments:
+ -h, --help show this help message and exit
+ -v, --verbose increase output verbosity
+
+Note that the new ability is also reflected in the help text.
+
+
+Combining Positional and Optional arguments
+===========================================
+
+Our program keeps growing in complexity::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", type=int,
+ help="display a square of a given number")
+ parser.add_argument("-v", "--verbose", action="store_true",
+ help="increase output verbosity")
+ args = parser.parse_args()
+ answer = pow(args.square, 2)
+ if args.verbose:
+ print("the square of {} equals {}".format(args.square, answer))
+ else:
+ print(answer)
+
+And now the output::
+
+ $ python3 prog.py
+ usage: prog.py [-h] [-v] square
+ prog.py: error: the following arguments are required: square
+ $ python3 prog.py 4
+ 16
+ $ python3 prog.py 4 --verbose
+ the square of 4 equals 16
+ $ python3 prog.py --verbose 4
+ the square of 4 equals 16
+
+* We've brought back a positional argument, hence the complaint.
+
+* As for the fourth output, note that the order does not matter.
+
+How about we give this program of ours back the ability to have
+multiple verbosity values, and actually get to use them::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", type=int,
+ help="display a square of a given number")
+ parser.add_argument("-v", "--verbosity", type=int,
+ help="increase output verbosity")
+ args = parser.parse_args()
+ answer = pow(args.square, 2)
+ if args.verbosity == 2:
+ print("the square of {} equals {}".format(args.square, answer))
+ elif args.verbosity == 1:
+ print("pow({}, 2) == {}".format(args.square, answer))
+ else:
+ print(answer)
+
+And the output::
+
+ $ python3 prog.py 4
+ 16
+ $ python3 prog.py 4 -v
+ usage: prog.py [-h] [-v VERBOSITY] square
+ prog.py: error: argument -v/--verbosity: expected one argument
+ $ python3 prog.py 4 -v 1
+ pow(4, 2) == 16
+ $ python3 prog.py 4 -v 2
+ the square of 4 equals 16
+ $ python3 prog.py 4 -v 3
+ 16
+
+These all look good except the last one, which exposes a bug in our program.
+Let's fix it by restricting the values the ``--verbosity`` option can accept::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", type=int,
+ help="display a square of a given number")
+ parser.add_argument("-v", "--verbosity", type=int, choices=[0, 1, 2],
+ help="increase output verbosity")
+ args = parser.parse_args()
+ answer = pow(args.square, 2)
+ if args.verbosity == 2:
+ print("the square of {} equals {}".format(args.square, answer))
+ elif args.verbosity == 1:
+ print("pow({}, 2) == {}".format(args.square, answer))
+ else:
+ print(answer)
+
+And the output::
+
+ $ python3 prog.py 4 -v 3
+ usage: prog.py [-h] [-v {0,1,2}] square
+ prog.py: error: argument -v/--verbosity: invalid choice: 3 (choose from 0, 1, 2)
+ $ python3 prog.py 4 -h
+ usage: prog.py [-h] [-v {0,1,2}] square
+
+ positional arguments:
+ square display a square of a given number
+
+ optional arguments:
+ -h, --help show this help message and exit
+ -v {0,1,2}, --verbosity {0,1,2}
+ increase output verbosity
+
+Note that the change also reflects both in the error message as well as the
+help string.
+
+Now, let's use a different approach of playing with verbosity, which is pretty
+common. It also matches the way the CPython executable handles its own
+verbosity argument (check the output of `python --help`)::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", type=int,
+ help="display a square of a given number")
+ parser.add_argument("-v", "--verbosity", action="count",
+ help="increase output verbosity")
+ args = parser.parse_args()
+ answer = pow(args.square, 2)
+ if args.verbosity == 2:
+ print("the square of {} equals {}".format(args.square, answer))
+ elif args.verbosity == 1:
+ print("pow({}, 2) == {}".format(args.square, answer))
+ else:
+ print(answer)
+
+We have introduced another action, "count". What it does is keep a count of
+optional arguments::
+
+ $ python3 prog.py 4 -v 1
+ usage: prog.py [-h] [-v] square
+ prog.py: error: unrecognized arguments: 1
+ $ python3 prog.py 4 -v
+ pow(4, 2) == 16
+ $ python3 prog.py 4 -vv
+ the square of 4 equals 16
+ $ python3 prog.py 4
+ 16
+ $ python3 prog.py 4 --verbosity --verbosity
+ the square of 4 equals 16
+ $ python3 prog.py 4 -h
+ usage: prog.py [-h] [-v] square
+
+ positional arguments:
+ square display a square of a given number
+
+ optional arguments:
+ -h, --help show this help message and exit
+ -v, --verbosity increase output verbosity
+ $ python3 prog.py 4 -vvv
+ 16
+
+* Yes, it's now more of a flag (similar tp `action="store_true"`) in the
+ previous version of our script. That should explain the complaint.
+* See what I mean that it behaves similar to "store_true" action?
+* Now here's a demonstration of what the "count" action gives. You've probably
+ seen this sort of usage before.
+* And, just like the "store_true" action, if you don't specify the `-v` flag,
+ that flag is considered to have ``None`` value.
+* As should be expected, specifying the long form of the flag, we should get
+ the same output.
+* Sadly, our help output isn't very informative on the new ability our script
+ has acquired, but that can always be fixed by improving the documentation for
+ out script (e.g. via the `help` keyword argument).
+* That's a bug in our program.
+
+Let's fix::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", type=int,
+ help="display a square of a given number")
+ parser.add_argument("-v", "--verbosity", action="count",
+ help="increase output verbosity")
+ args = parser.parse_args()
+ answer = pow(args.square, 2)
+ if args.verbosity >= 2:
+ print("the square of {} equals {}".format(args.square, answer))
+ elif args.verbosity >= 1:
+ print("pow({}, 2) == {}".format(args.square, answer))
+ else:
+ print(answer)
+
+And this is what it gives::
+
+ $ python3 prog.py 4 -vvv
+ the square of 4 equals 16
+ $ python3 prog.py 4 -vvvv
+ the square of 4 equals 16
+ $ python3 prog.py 4
+ Traceback (most recent call last):
+ File "prog.py", line 11, in <module>
+ if args.verbosity >= 2:
+ TypeError: unorderable types: NoneType() >= int()
+
+* First output went as well, and fixes the bug we had before. That is, to avoid
+ such problems, do `>=` checks in future, not `==`.
+* Third output not so good
+
+Let's fix that bug::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("square", type=int,
+ help="display a square of a given number")
+ parser.add_argument("-v", "--verbosity", action="count", default=0,
+ help="increase output verbosity")
+ args = parser.parse_args()
+ answer = pow(args.square, 2)
+ if args.verbosity >= 2:
+ print("the square of {} equals {}".format(args.square, answer))
+ elif args.verbosity >= 1:
+ print("pow({}, 2) == {}".format(args.square, answer))
+ else:
+ print(answer)
+
+We've just introduced yet another keyword, `default`. We've set it to `0` in
+order to make it comparable to the other int values. Remember that by
+default, if an optional argument isn't specified, it gets the `None` value, and
+that cannot be compared to an int value (hence the :exc:`TypeError` exception).
+
+And::
+
+ $ python3 prog.py 4
+ 16
+
+You can go quite far just with what we've learned so, and we have only
+scratched the surface. The :mod:`argparse` module is excessively powerful, and
+we'll explore a bit more of it before we end this tutorial.
+
+
+Getting a little more advanced
+==============================
+
+What if we wanted to expand our tiny program to perform other powers, not
+just 2::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("power", type=int, nargs=2)
+ parser.add_argument("-v", "--verbosity", action="count", default=0)
+ args = parser.parse_args()
+ answer = pow(args.power[0], args.power[1])
+ if args.verbosity >= 2:
+ print("{} to the power {} equals {}".format(args.power[0], args.power[1], answer))
+ elif args.verbosity >= 1:
+ print("pow({}, {}) == {}".format(args.power[0], args.power[1], answer))
+ else:
+ print(answer)
+
+Output::
+
+ $ python3 prog.py
+ usage: prog.py [-h] [-v] power power
+ prog.py: error: the following arguments are required: power
+ $ python3 prog.py -h
+ usage: prog.py [-h] [-v] power power
+
+ positional arguments:
+ power
+
+ optional arguments:
+ -h, --help show this help message and exit
+ -v, --verbosity
+ $ python3 prog.py 4 2
+ 16
+ $ python3 prog.py 4 2 -v
+ pow(4, 2) == 16
+ $ python3 prog.py 4 2 -vv
+ 4 to the power 2 equals 16
+ $ python3 prog.py 4 2 -vvv
+ 4 to the power 2 equals 16
+
+We introduced yet another keyword argument, ``nargs``. It helps us specify
+how many arguments are expected for a given command line option, which is
+2 in this case.
+
+As you can see, the help text could be a little better than what it is
+(``usage: prog.py [-h] [-v {0,1,2}] power power``). Let's fix it::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("x", type=int, help="the 'x' in x^y")
+ parser.add_argument("y", type=int, help="the 'y' in x^y")
+ parser.add_argument("-v", "--verbosity", action="count", default=0)
+ args = parser.parse_args()
+ answer = pow(args.x, args.y)
+ if args.verbosity >= 2:
+ print("{} to the power {} equals {}".format(args.x, args.y, answer))
+ elif args.verbosity >= 1:
+ print("pow({}, {}) == {}".format(args.x, args.y, answer))
+ else:
+ print(answer)
+
+Output::
+
+ $ python3 prog.py
+ usage: prog.py [-h] [-v] x y
+ prog.py: error: the following arguments are required: x, y
+ $ python3 prog.py -h
+ usage: prog.py [-h] [-v] x y
+
+ positional arguments:
+ x the 'x' in x^y
+ y the 'y' in x^y
+
+ optional arguments:
+ -h, --help show this help message and exit
+ -v, --verbosity
+ $ python3 prog.py 4 2 -v
+ pow(4, 2) == 16
+ $ python3 prog.py 4 2 -v 1
+ usage: prog.py [-h] [-v] x y
+ prog.py: error: argument -v/--verbosity: ignored explicit argument '1'
+
+That looks much better, and the last example serves as a reminder that this
+is pretty much a flag, removing the need to provide values.
+
+Notice that so far we've been using verbosity level to *change* the text
+that gets displayed. The following example instead uses verbosity level
+to display *more* text instead::
+
+ import argparse
+ parser = argparse.ArgumentParser()
+ parser.add_argument("x", type=int, help="the 'x' in x^y")
+ parser.add_argument("y", type=int, help="the 'y' in x^y")
+ parser.add_argument("-v", "--verbosity", action="count", default=0)
+ args = parser.parse_args()
+ answer = pow(args.x, args.y)
+ if args.verbosity >= 2:
+ print("Running '{}'".format(__file__))
+ if args.verbosity >= 1:
+ print("pow({}, {}) == ".format(args.x, args.y), end="")
+ print(answer)
+
+Output::
+
+ $ python3 prog.py 4 2
+ 16
+ $ python3 prog.py 4 2 -v
+ pow(4, 2) == 16
+ $ python3 prog.py 4 2 -vv
+ Running 'prog.py'
+ pow(4, 2) == 16
+
+So far, we have been working with two methods of an
+:class:`argparse.ArgumentParser` instance. Let's introduce a third one,
+``add_mutually_exclusive_group``. It allows for us to specify options that
+conflict with each other. Let's also change the rest of the program make the
+new functionality makes more sense::
+
+ import argparse
+
+ parser = argparse.ArgumentParser()
+ group = parser.add_mutually_exclusive_group()
+ group.add_argument("-v", "--verbose", action="store_true")
+ group.add_argument("-q", "--quiet", action="store_true")
+ parser.add_argument("x", type=int, help="the 'x' in x^y")
+ parser.add_argument("y", type=int, help="the 'y' in x^y")
+ args = parser.parse_args()
+ answer = pow(args.x, args.y)
+
+ if args.quiet:
+ print(answer)
+ elif args.verbose:
+ print("{} to the power {} equals {}".format(args.x, args.y, answer))
+ else:
+ print("pow({}, {}) == {}".format(args.x, args.y, answer))
+
+Our program is now simpler, and we've lost some functionality for the sake of
+demonstration. Anyways, here's the output::
+
+ $ python3 prog.py 4 2
+ pow(4, 2) == 16
+ $ python3 prog.py 4 2 -q
+ 16
+ $ python3 prog.py 4 2 -v
+ 4 to the power 2 equals 16
+ $ python3 prog.py 4 2 -vq
+ usage: prog.py [-h] [-v | -q] x y
+ prog.py: error: argument -q/--quiet: not allowed with argument -v/--verbose
+ $ python3 prog.py 4 2 -v --quiet
+ usage: prog.py [-h] [-v | -q] x y
+ prog.py: error: argument -q/--quiet: not allowed with argument -v/--verbose
+
+That should be easy to follow. I've added that last output so you can see the
+sort of flexibility you get, i.e. mixing long form options with short form
+ones.
+
+Before we conclude, you probably want to tell your users the main purpose of
+your program, just in case they don't know::
+
+ import argparse
+
+ parser = argparse.ArgumentParser(description="calculate X to the power of Y")
+ group = parser.add_mutually_exclusive_group()
+ group.add_argument("-v", "--verbose", action="store_true")
+ group.add_argument("-q", "--quiet", action="store_true")
+ parser.add_argument("x", type=int, help="the 'x' in x^y")
+ parser.add_argument("y", type=int, help="the 'y' in x^y")
+ args = parser.parse_args()
+ answer = pow(args.x, args.y)
+
+ if args.quiet:
+ print(answer)
+ elif args.verbose:
+ print("{} to the power {} equals {}".format(args.x, args.y, answer))
+ else:
+ print("pow({}, {}) == {}".format(args.x, args.y, answer))
+
+Which outputs::
+
+ $ python3 prog.py --help
+ usage: prog.py [-h] [-v | -q] x y
+
+ calculate X to the power of Y
+
+ positional arguments:
+ x the 'x' in x^y
+ y the 'y' in x^y
+
+ optional arguments:
+ -h, --help show this help message and exit
+ -v, --verbose
+ -q, --quiet
+
+Note that slight difference in the usage text. Note the `[-v | -q]`, which
+tells us that we can either use `-v` or `-q`, but not both at the same time.
+
+Conclusion
+==========
+
+There's lots more to the module of course, things like customising
+the help message, or simply disabling its getting generated.
+You can also force optional arguments to be required, or even change the
+character used to denote them (e.g. ``+v`` instead of ``-v``).
+
+Have a look at the API docs.
+They are quite detailed and thorough, and full of examples. I hope that
+having gone through this tutorial, you will easily digest them
+without feeling overwhelmed.
diff --git a/Doc/howto/index.rst b/Doc/howto/index.rst
--- a/Doc/howto/index.rst
+++ b/Doc/howto/index.rst
@@ -27,4 +27,5 @@
unicode.rst
urllib2.rst
webservers.rst
+ argparse.rst
diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -10,6 +10,12 @@
**Source code:** :source:`Lib/argparse.py`
+.. sidebar:: Tutorial
+
+ This page contains the API reference information. For a more gentle
+ introduction to Python command line parsing, have a look at the
+ :ref:`Basic Tutorial <argparse-howto>`.
+
--------------
The :mod:`argparse` module makes it easy to write user-friendly command-line
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