diff --git a/Lib/argparse.py b/Lib/argparse.py
index e45b67b67704a9..60fef61922dbf7 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -404,13 +404,19 @@ def _format_actions_usage(self, actions, groups):
inserts[start] += ' ['
else:
inserts[start] = '['
- inserts[end] = ']'
+ if end in inserts:
+ inserts[end] += ']'
+ else:
+ inserts[end] = ']'
else:
if start in inserts:
inserts[start] += ' ('
else:
inserts[start] = '('
- inserts[end] = ')'
+ if end in inserts:
+ inserts[end] += ')'
+ else:
+ inserts[end] = ')'
for i in range(start + 1, end):
inserts[i] = '|'
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 5128dc5e1be499..707d3215b24792 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -2813,6 +2813,46 @@ def get_parser(self, required):
-c c help
'''
+class TestMutuallyExclusiveNested(MEMixin, TestCase):
+
+ def get_parser(self, required):
+ parser = ErrorRaisingArgumentParser(prog='PROG')
+ group = parser.add_mutually_exclusive_group(required=required)
+ group.add_argument('-a')
+ group.add_argument('-b')
+ group2 = group.add_mutually_exclusive_group(required=required)
+ group2.add_argument('-c')
+ group2.add_argument('-d')
+ group3 = group2.add_mutually_exclusive_group(required=required)
+ group3.add_argument('-e')
+ group3.add_argument('-f')
+ return parser
+
+ usage_when_not_required = '''\
+ usage: PROG [-h] [-a A | -b B | [-c C | -d D | [-e E | -f F]]]
+ '''
+ usage_when_required = '''\
+ usage: PROG [-h] (-a A | -b B | (-c C | -d D | (-e E | -f F)))
+ '''
+
+ help = '''\
+
+ optional arguments:
+ -h, --help show this help message and exit
+ -a A
+ -b B
+ -c C
+ -d D
+ -e E
+ -f F
+ '''
+
+ # We are only interested in testing the behavior of format_usage().
+ test_failures_when_not_required = None
+ test_failures_when_required = None
+ test_successes_when_not_required = None
+ test_successes_when_required = None
+
# =================================================
# Mutually exclusive group in parent parser tests
# =================================================
diff --git a/Misc/NEWS.d/next/Library/2019-07-27-10-14-45.bpo-29553.TVeIDe.rst b/Misc/NEWS.d/next/Library/2019-07-27-10-14-45.bpo-29553.TVeIDe.rst
new file mode 100644
index 00000000000000..3472db7bf20998
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-07-27-10-14-45.bpo-29553.TVeIDe.rst
@@ -0,0 +1,2 @@
+Fixed :meth:`argparse.ArgumentParser.format_usage` for mutually exclusive groups.
+Patch by Andrew Nester.
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