- Issue #15906: Fix a regression in argparse caused by the preceding change,
when action='append', type='str' and default=[].
diff --git a/Lib/argparse.py b/Lib/argparse.py
index ab8ff2f..440d8fa 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -1948,6 +1948,7 @@
# twice (which may fail) if the argument was given, but
# only if it was defined already in the namespace
if (action.default is not None and
+ isinstance(action, _StoreAction) and
hasattr(namespace, action.dest) and
action.default is getattr(namespace, action.dest)):
setattr(namespace, action.dest,
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 99c1bab..c611944 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -4480,6 +4480,16 @@
args = parser.parse_args([])
self.assertEqual(NS(foo='foo_converted'), args)
+ def test_issue_15906(self):
+ # Issue #15906: When action='append', type=str, default=[] are
+ # providing, the dest value was the string representation "[]" when it
+ # should have been an empty list.
+ parser = argparse.ArgumentParser()
+ parser.add_argument('--test', dest='test', type=str,
+ default=[], action='append')
+ args = parser.parse_args([])
+ self.assertEqual(args.test, [])
+
# ======================
# parse_known_args tests
# ======================