Fix mutable default arguments in XMLWriter

llukito · llukito · commit fded0d55b5fb · 2026-02-13T07:52:12.000Z
diff --git a/lib/matplotlib/backends/backend_svg.py b/lib/matplotlib/backends/backend_svg.py
@@ -133,7 +133,7 @@ def __flush(self, indent=True):
             self.__write(_escape_cdata(data))
             self.__data = []
 
-    def start(self, tag, attrib={}, **extra):
+    def start(self, tag, attrib=None, **extra):
         """
         Open a new element.  Attributes can be given as keyword
         arguments, or as a string/string dictionary. The method returns
@@ -152,6 +152,8 @@ def start(self, tag, attrib={}, **extra):
         -------
         An element identifier.
         """
+        if attrib is None:
+            attrib = {}
         self.__flush()
         tag = _escape_cdata(tag)
         self.__data = []
@@ -232,12 +234,14 @@ def close(self, id):
         while len(self.__tags) > id:
             self.end()
 
-    def element(self, tag, text=None, attrib={}, **extra):
+    def element(self, tag, text=None, attrib=None, **extra):
         """
         Add an entire element.  This is the same as calling :meth:`start`,
         :meth:`data`, and :meth:`end` in sequence. The *text* argument can be
         omitted.
         """
+        if attrib is None:
+            attrib = {}
         self.start(tag, attrib, **extra)
         if text:
             self.data(text)
