#10777: fix iteration over dict keys while mutating the dict.
diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index 08f7988..22fafa9 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -1841,6 +1841,15 @@
"""
+def check_issue10777():
+ """
+ Registering a namespace twice caused a "dictionary changed size during
+ iteration" bug.
+
+ >>> ET.register_namespace('test10777', 'http://myuri/')
+ >>> ET.register_namespace('test10777', 'http://myuri/')
+ """
+
# --------------------------------------------------------------------
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index 53aa9e7..ba33879 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -1068,7 +1068,7 @@
def register_namespace(prefix, uri):
if re.match("ns\d+$", prefix):
raise ValueError("Prefix format reserved for internal use")
- for k, v in _namespace_map.items():
+ for k, v in list(_namespace_map.items()):
if k == uri or v == prefix:
del _namespace_map[k]
_namespace_map[uri] = prefix
diff --git a/Misc/NEWS b/Misc/NEWS
index 8acc9e3..46b6233 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -18,6 +18,9 @@
Library
-------
+- Issue #10777: Fix "dictionary changed size during iteration" bug in
+ ElementTree register_namespace().
+
- Issue #10626: test_logging now preserves logger disabled states.
- Issue #10774: test_logging now removes temp files created during tests.