mirror of https://github.com/python/cpython
56 lines
2.3 KiB
ReStructuredText
56 lines
2.3 KiB
ReStructuredText
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.. currentmodule:: argparse
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.. _upgrading-optparse-code:
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==========================
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Upgrading optparse code
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==========================
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Originally, the :mod:`argparse` module had attempted to maintain compatibility
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with :mod:`optparse`. However, :mod:`optparse` was difficult to extend
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transparently, particularly with the changes required to support
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``nargs=`` specifiers and better usage messages. When most everything in
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:mod:`optparse` had either been copy-pasted over or monkey-patched, it no
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longer seemed practical to try to maintain the backwards compatibility.
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The :mod:`argparse` module improves on the :mod:`optparse`
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module in a number of ways including:
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* Handling positional arguments.
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* Supporting subcommands.
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* Allowing alternative option prefixes like ``+`` and ``/``.
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* Handling zero-or-more and one-or-more style arguments.
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* Producing more informative usage messages.
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* Providing a much simpler interface for custom ``type`` and ``action``.
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A partial upgrade path from :mod:`optparse` to :mod:`argparse`:
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* Replace all :meth:`optparse.OptionParser.add_option` calls with
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:meth:`ArgumentParser.add_argument` calls.
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* Replace ``(options, args) = parser.parse_args()`` with ``args =
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parser.parse_args()`` and add additional :meth:`ArgumentParser.add_argument`
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calls for the positional arguments. Keep in mind that what was previously
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called ``options``, now in the :mod:`argparse` context is called ``args``.
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* Replace :meth:`optparse.OptionParser.disable_interspersed_args`
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by using :meth:`~ArgumentParser.parse_intermixed_args` instead of
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:meth:`~ArgumentParser.parse_args`.
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* Replace callback actions and the ``callback_*`` keyword arguments with
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``type`` or ``action`` arguments.
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* Replace string names for ``type`` keyword arguments with the corresponding
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type objects (e.g. int, float, complex, etc).
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* Replace :class:`optparse.Values` with :class:`Namespace` and
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:exc:`optparse.OptionError` and :exc:`optparse.OptionValueError` with
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:exc:`ArgumentError`.
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* Replace strings with implicit arguments such as ``%default`` or ``%prog`` with
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the standard Python syntax to use dictionaries to format strings, that is,
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``%(default)s`` and ``%(prog)s``.
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* Replace the OptionParser constructor ``version`` argument with a call to
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``parser.add_argument('--version', action='version', version='<the version>')``.
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