Support defaultdict for namespace mapping (#211)

tests/test_xmltodict.py

@@ -1,4 +1,5 @@
 from xmltodict import parse, ParsingInterrupted
+import collections
 import unittest
 
 try:
@@ -227,6 +228,35 @@ def test_namespace_collapse(self):
         res = parse(xml, process_namespaces=True, namespaces=namespaces)
         self.assertEqual(res, d)
 
+    def test_namespace_collapse_all(self):
+        xml = """
+        <root xmlns="http://defaultns.com/"
+              xmlns:a="http://a.com/"
+              xmlns:b="http://b.com/">
+          <x a:attr="val">1</x>
+          <a:y>2</a:y>
+          <b:z>3</b:z>
+        </root>
+        """
+        namespaces = collections.defaultdict(lambda: None)
+        d = {
+            'root': {
+                'x': {
+                    '@xmlns': {
+                        '': 'http://defaultns.com/',
+                        'a': 'http://a.com/',
+                        'b': 'http://b.com/',
+                    },
+                    '@attr': 'val',
+                    '#text': '1',
+                },
+                'y': '2',
+                'z': '3',
+            },
+        }
+        res = parse(xml, process_namespaces=True, namespaces=namespaces)
+        self.assertEqual(res, d)
+
     def test_namespace_ignore(self):
         xml = """
         <root xmlns="http://defaultns.com/"

xmltodict.py

@@ -70,13 +70,16 @@ def __init__(self,
         self.force_list = force_list
 
     def _build_name(self, full_name):
-        if not self.namespaces:
+        if self.namespaces is None:
             return full_name
         i = full_name.rfind(self.namespace_separator)
         if i == -1:
             return full_name
         namespace, name = full_name[:i], full_name[i+1:]
-        short_namespace = self.namespaces.get(namespace, namespace)
+        try:
+            short_namespace = self.namespaces[namespace]
+        except KeyError:
+            short_namespace = namespace
         if not short_namespace:
             return name
         else: