python-openxml
diff --git a/‎opc/pkgreader.py‎
Lines changed: 19 additions & 0 deletions b/‎opc/pkgreader.py‎
Lines changed: 19 additions & 0 deletions
diff --git a/‎tests/test_pkgreader.py‎
Lines changed: 28 additions & 0 deletions b/‎tests/test_pkgreader.py‎
Lines changed: 28 additions & 0 deletions
@@ -101,6 +101,25 @@ class _ContentTypeMap(object):
     Value type providing dictionary semantics for looking up content type by
     part name, e.g. ``content_type = cti['/ppt/presentation.xml']``.
     """
+    def __init__(self):
+        super(_ContentTypeMap, self).__init__()
+        self._overrides = dict()
+        self._defaults = dict()
+
+    def __getitem__(self, partname):
+        """
+        Return content type for part identified by *partname*.
+        """
+        if not isinstance(partname, PackURI):
+            tmpl = "_ContentTypeMap key must be <type 'PackURI'>, got %s"
+            raise KeyError(tmpl % type(partname))
+        if partname in self._overrides:
+            return self._overrides[partname]
+        if partname.ext in self._defaults:
+            return self._defaults[partname.ext]
+        tmpl = "no content type for partname '%s' in [Content_Types].xml"
+        raise KeyError(tmpl % partname)
+
     @staticmethod
     def from_xml(content_types_xml):
         """
 
@@ -14,6 +14,7 @@
 from mock import call, Mock, patch
 
 from opc.constants import RELATIONSHIP_TARGET_MODE as RTM
+from opc.packuri import PackURI
 from opc.phys_pkg import ZipPkgReader
 from opc.pkgreader import (
     _ContentTypeMap, PackageReader, _SerializedRelationship,
@@ -230,6 +231,33 @@ def it_can_construct_from_types_xml(self, oxml_fromstring):
         assert ct_map._overrides == expected_overrides
         assert ct_map._defaults == expected_defaults
 
+    def it_matches_overrides(self):
+        # test data --------------------
+        partname = PackURI('/part/name1.xml')
+        content_type = 'app/vnd.type1'
+        # fixture ----------------------
+        ct_map = _ContentTypeMap()
+        ct_map._overrides = {partname: content_type}
+        # verify -----------------------
+        assert ct_map[partname] == content_type
+
+    def it_falls_back_to_defaults(self):
+        ct_map = _ContentTypeMap()
+        ct_map._overrides = {PackURI('/part/name1.xml'): 'app/vnd.type1'}
+        ct_map._defaults = {'.xml': 'application/xml'}
+        assert ct_map[PackURI('/part/name2.xml')] == 'application/xml'
+
+    def it_should_raise_on_partname_not_found(self):
+        ct_map = _ContentTypeMap()
+        with pytest.raises(KeyError):
+            ct_map[PackURI('/!blat/rhumba.1x&')]
+
+    def it_should_raise_on_key_not_instance_of_PackURI(self):
+        ct_map = _ContentTypeMap()
+        ct_map._overrides = {PackURI('/part/name1.xml'): 'app/vnd.type1'}
+        with pytest.raises(KeyError):
+            ct_map['/part/name1.xml']
+
 
 class Describe_SerializedRelationship(object):