Updates based on Serhiy's feedback

python · ncoghlan · Dec 23, 2024 · Oct 31, 2024 · Oct 31, 2024 · Oct 31, 2024
commit 93d7161893a84656403365098a2d04f0d1434a36
@@ -6,15 +6,8 @@
 Upgrading optparse code
 ==========================
 
-Originally, the :mod:`argparse` module had attempted to maintain compatibility
-with :mod:`optparse`.  However, :mod:`optparse` was difficult to extend
-transparently, particularly with the changes required to support
-``nargs=`` specifiers and better usage messages.  When most everything in
-:mod:`optparse` had either been copy-pasted over or monkey-patched, it no
-longer seemed practical to try to maintain the backwards compatibility.
-
-The :mod:`argparse` module improves on the :mod:`optparse`
-module in a number of ways including:
+The :mod:`argparse` module offers several higher level features not natively
+provided by the :mod:`optparse` module, including:
 
 * Handling positional arguments.
 * Supporting subcommands.
@@ -23,6 +16,13 @@ module in a number of ways including:
 * Producing more informative usage messages.
 * Providing a much simpler interface for custom ``type`` and ``action``.
 
+Originally, the :mod:`argparse` module attempted to maintain compatibility
+with :mod:`optparse`.  However, :mod:`optparse` was difficult to extend
+transparently, particularly with the changes required to support
+``nargs=`` specifiers and better usage messages.  When most everything in
+:mod:`optparse` had either been copy-pasted over or monkey-patched, it no
+longer seemed practical to try to maintain the backwards compatibility.
+
 A partial upgrade path from :mod:`optparse` to :mod:`argparse`:
 
 * Replace all :meth:`optparse.OptionParser.add_option` calls with

@@ -13,11 +13,15 @@ recommended command-line parsing module in the Python standard library.
 
 .. note::
 
-   There are two other modules that fulfill the same task, namely
-   :mod:`getopt` (an equivalent for ``getopt()`` from the C
-   language) and the lower level :mod:`optparse` module.
-   Note also that :mod:`argparse` is based on :mod:`optparse`,
-   and therefore very similar in terms of usage.
+   The standard library includes two other libraries directly related
+   to command-line parameter processing: the lower level :mod:`optparse`
+   module (which may require more code to configure for a given application,
+   but also allows an application to request behaviors that ``argparse``
+   doesn't support), and the very low level :mod:`getopt` (which specifically
+   serves as an equivalent to ``getopt()`` from the C language).
+   While neither of those modules is covered directly in this guide, many of
+   the core concepts in ``argparse`` first originated in ``optparse``, so
+   some aspects of this tutorial will also be relevant to ``optparse`` users.
 
 
 Concepts

@@ -19,9 +19,11 @@
    lower level :mod:`optparse` module serves as a better foundation for
    that use case. ``optparse`` (or one of the third party libraries
    based on it) may also be worth considering for applications where
-   stricter adherence to common Unix and Linux command line interface
-   conventions around the handling of option parameter values that start
-   with ``-`` is desired.
+   ``argparse`` doesn't support behaviors that the application requires
+   (such as entirely disabling support for interspersed options and
+   positional arguments, or stricter adherence to common Unix and Linux
+   command line interface conventions related to the handling of option
+   parameter values that start with ``-``).
 
 --------------
 

diff --git a/Doc/library/getopt.rst b/Doc/library/getopt.rst
@@ -9,11 +9,11 @@
 
 .. note::
 
-   The :mod:`getopt` module is a parser for command line options whose API is
-   designed to be familiar to users of the C :c:func:`!getopt` function. Users who
-   are unfamiliar with the C :c:func:`!getopt` function or who would like to write
-   less code and get better help and error messages should consider using the
-   :mod:`argparse` module instead.
+   This module is considered feature complete. A more object-oriented and
+   extensible alternative to this API is provided in the :mod:`optparse`
+   module. Further functional enhancements for command line parameter
+   processing are provided either as third party modules on PyPI,
+   or else as features in the :mod:`argparse` module.
 
 --------------
 
@@ -23,6 +23,12 @@
 options similar to those supported by GNU software may be used as well via an
 optional third argument.
 
+Users who are unfamiliar with the Unix :c:func:`!getopt` function should consider
+using the :mod:`argparse` module instead. Users who are familiar with the Unix
+:c:func:`!getopt` function, but would like to get equivalent behavior while
+writing less code and getting better help and error messages should consider
+using the :mod:`optparse` module.
+
 This module provides two functions and an
 exception:
 
@@ -150,29 +156,49 @@
    import optparse
 
    if __name__ == '__main__':
-       parser = optparse.OptionParser()
-       parser.add_option('-o', '--output')
-       parser.add_option('-v', dest='verbose', action='store_true')
-       opts, args = parser.parse_args()
-       process(args, output=opts.output, verbose=opts.verbose)
-
-An equivalent command line interface for this simple case can also be produced
-by using the :mod:`argparse` module::
-
-   import argparse
-
-   if __name__ == '__main__':
-       parser = argparse.ArgumentParser()
-       parser.add_argument('-o', '--output')
-       parser.add_argument('-v', dest='verbose', action='store_true')
-       args = parser.parse_args()
-       # ... do something with args.output ...
-       # ... do something with args.verbose ..
-
-In more complex cases (such as options which accept values), the behaviour
-of the ``argparse`` version may diverge from that of the ``getopt`` and
-``optparse`` versions due to the way ``argparse`` handles parameter
-values that start with ``-``.
+         parser = optparse.OptionParser()
+         parser.add_option('-o', '--output')
+         parser.add_option('-v', dest='verbose', action='store_true')
+         opts, args = parser.parse_args()
+         process(args, output=opts.output, verbose=opts.verbose)
+
+A roughly equivalent command line interface for this case can also be
+produced by using the :mod:`argparse` module::
+
+import argparse
+
+if __name__ == '__main__':
+      parser = argparse.ArgumentParser()
+      parser.add_argument('-o', '--output')
+      parser.add_argument('-v', dest='verbose', action='store_true')
+      parser.add_argument('rest', nargs='*')
+      args = parser.parse_args()
+      process(args.rest, output=args.output, verbose=args.verbose)
+
+However, unlike the ``optparse`` example, this ``argparse`` example will
+handle some parameter combinations differently from the way the ``getopt``
+version would handle them. For example (amongst other differences):
+
+* supplying ``-o -v`` gives ``output="-v"`` and ``verbose=False``
+  for both ``getopt`` and ``optparse``,
+  but a usage error with ``argparse``
+  (complaining that no value has been supplied for ``-o/--output``,
+  since ``-v`` is interpreted as meaning the verbosity flag)
+* similarly, supplying ``-o --`` gives ``output="--"`` and ``args=()``
+  for both ``getopt`` and ``optparse``,
+  but a usage error with ``argparse``
+  (also complaining that no value has been supplied for ``-o/--output``,
+  since ``--`` is interpreted as terminating the option processing
+  and treating all remaining values as positional arguments)
+* supplying ``-o=foo`` gives ``output="=foo"``
+  for both ``getopt`` and ``optparse``,
+  but gives ``output="foo"`` with ``argparse``
+  (since ``=`` is special cased as an alternative separator for
+  option parameter values)
+
+Whether these differing behaviors in the ``argparse`` version are
+considered desirable or a problem will depend on the specific command line
+application use case.
 
 .. seealso::
 

diff --git a/Doc/library/optparse.rst b/Doc/library/optparse.rst
@@ -12,8 +12,14 @@
 
 .. note::
 
-   :mod:`argparse` (rather than this module) is the recommended standard
-   library module for implementing command line applications unless one
+   This module is considered feature complete. Further functional enhancements for
+   command line parameter processing are provided either as third party modules on
+   PyPI, or else as features in the :mod:`argparse` module.
+
+.. note::
+
+   The higher level :mod:`argparse` (rather than this module) is the recommended
+   standard library module for implementing command line applications unless one
    of the following caveats applies:
 
    * the application requires additional control over the way options and
@@ -24,24 +30,24 @@
      exact way it works in practice is undesirable for some use cases)
    * the application requires additional control over the handling of options
      which accept parameter values that may start with ``-`` (such as delegated
-     options to be passed to invoked subprocesses).
+     options to be passed to invoked subprocesses)
+   * the application requires some other command line parameter processing
+     behavior which ``argparse`` does not support, but which can be implemented
+     in terms of the lower level interface offered by ``optparse``
 
    These ``argparse`` caveats also mean that :mod:`optparse` is likely to
    provide a better foundation for library authors *writing* third party
    command line argument processing libraries.
 
 .. seealso::
 
-    The :pypi:`"click" package <click>` is an ``optparse`` based third party
-    argument processing library which allows command line applications to be
-    developed as a set of appropriately decorated command implementation
-    functions.
-
-.. se
69EF
ealso::
+    :pypi:`click` is a third party argument processing library (originally
+    based on ``optparse``), which allows command line applications to be
+    developed as a set of decorated command implementation functions.
 
-    The :pypi:`"Typer" package <click>` is a ``click`` based third party
-    argument processing library which allows the use of annotated Python
-    type hints to define an application's command line interface.
+    Other third party libraries, such as :pypi:`typer` or :pypi:`msgspec-click`,
+    allow command line interfaces to be specified in ways that effectively
+    integrate with static checking of Python type annotations.
 
 --------------