Computed answers are run through safe_exec.

common/lib/capa/capa/responsetypes.py

@@ -1087,8 +1087,7 @@ def sympy_check2():
         # exec the check function
         if isinstance(self.code, basestring):
             try:
-                raise Exception("exec 1")
-                exec self.code in self.context['global_context'], self.context
+                safe_exec.safe_exec(self.code, self.context)
                 correct = self.context['correct']
                 messages = self.context['messages']
                 overall_message = self.context['overall_message']

common/test/data/embedded_python/course/2013_Spring.xml

@@ -92,6 +92,20 @@ print(num)
   </text>
 </problem>
 
+<problem url_name="computed_answer">
+
+  <customresponse>
+    <textline size="5" correct_answer="Xyzzy"/>
+    <answer type="loncapa/python">
+if submission[0] == "Xyzzy":
+    correct = ['correct']
+else:
+    correct = ['incorrect']
+    </answer>
+  </customresponse>
+
+</problem>
+
     </vertical>
   </chapter>
 </course>

lms/djangoapps/courseware/tests/tests.py

@@ -1023,3 +1023,8 @@ class TestSchematicResponse(TestSubmittingProblems):
         resp = self.submit_question_answer('cfn_problem', {'2_1': "xyzzy!"})
         respdata = json.loads(resp.content)
         self.assertEqual(respdata['success'], 'incorrect')
+
+    def test_computed_answer(self):
+        resp = self.submit_question_answer('computed_answer', {'2_1': "Xyzzy"})
+        respdata = json.loads(resp.content)
+        self.assertEqual(respdata['success'], 'correct')