bpo-9938: Add optional keyword argument exit_on_error to argparse.ArgumentParser (GH-15362)

Co-Authored-by: Xuanji Li <xuanji@gmail.com>


https://bugs.python.org/issue9938



Automerge-Triggered-By: @matrixise

1 files changed, 29 insertions, 1 deletions

diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index 368b1cf..c2cf7d3 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -142,7 +142,7 @@ ArgumentParser objects
                           formatter_class=argparse.HelpFormatter, \
                           prefix_chars='-', fromfile_prefix_chars=None, \
                           argument_default=None, conflict_handler='error', \
-                          add_help=True, allow_abbrev=True)
+                          add_help=True, allow_abbrev=True, exit_on_error=True)
 
    Create a new :class:`ArgumentParser` object. All parameters should be passed
    as keyword arguments. Each parameter has its own more detailed description
@@ -179,6 +179,9 @@ ArgumentParser objects
    * allow_abbrev_ - Allows long options to be abbreviated if the
      abbreviation is unambiguous. (default: ``True``)
 
+   * exit_on_error_ - Determines whether or not ArgumentParser exits with
+     error info when an error occurs. (default: ``True``)
+
    .. versionchanged:: 3.5
       *allow_abbrev* parameter was added.
 
@@ -186,6 +189,9 @@ ArgumentParser objects
       In previous versions, *allow_abbrev* also disabled grouping of short
       flags such as ``-vv`` to mean ``-v -v``.
 
+   .. versionchanged:: 3.9
+      *exit_on_error* parameter was added.
+
 The following sections describe how each of these are used.
 
 
@@ -647,6 +653,28 @@ the help options::
      +h, ++help  show this help message and exit
 
 
+exit_on_error
+^^^^^^^^^^^^^
+
+Normally, when you pass an invalid argument list to the :meth:`~ArgumentParser.parse_args`
+method of an :class:`ArgumentParser`, it will exit with error info.
+
+If the user would like catch errors manually, the feature can be enable by setting
+``exit_on_error`` to ``False``::
+
+   >>> parser = argparse.ArgumentParser(exit_on_error=False)
+   >>> parser.add_argument('--integers', type=int)
+   _StoreAction(option_strings=['--integers'], dest='integers', nargs=None, const=None, default=None, type=<class 'int'>, choices=None, help=None, metavar=None)
+   >>> try:
+   ...     parser.parse_args('--integers a'.split())
+   ... except argparse.ArgumentError:
+   ...     print('Catching an argumentError')
+   ...
+   Catching an argumentError
+
+.. versionadded:: 3.9
+
+
 The add_argument() method
 -------------------------