1 files changed, 65 insertions, 0 deletions
diff --git a/examples/console/evalcontext.py b/examples/console/evalcontext.py
new file mode 100644
index 0000000..70cd35f
--- /dev/null
+++ b/examples/console/evalcontext.py
@@ -0,0 +1,65 @@
+from cStringIO import StringIO
+import traceback
+import threading
+import pdb
+import sys
+
+exec_lock = threading.Lock()
+
+class EvalContext(object):
+
+    """
+    Class that represents a interactive interface.  It has its own
+    namespace.  Use eval_context.exec_expr(expr) to run commands; the
+    output of those commands is returned, as are print statements.
+
+    This is essentially what doctest does, and is taken directly from
+    doctest.
+    """
+
+    def __init__(self):
+        self.namespace = {}
+
+    def exec_expr(self, s):
+        out = StringIO()
+        exec_lock.acquire()
+        save_stdout = sys.stdout
+        try:
+            debugger = _OutputRedirectingPdb(save_stdout)
+            debugger.reset()
+            pdb.set_trace = debugger.set_trace
+            sys.stdout = out
+            try:
+                code = compile(s, '<web>', "single", 0, 1)
+                exec code in self.namespace
+                debugger.set_continue()
+            except KeyboardInterrupt:
+                raise
+            except:
+                traceback.print_exc(file=out)
+                debugger.set_continue()
+        finally:
+            sys.stdout = save_stdout
+            exec_lock.release()
+        return out.getvalue()
+
+# From doctest
+class _OutputRedirectingPdb(pdb.Pdb):
+    """
+    A specialized version of the python debugger that redirects stdout
+    to a given stream when interacting with the user.  Stdout is *not*
+    redirected when traced code is executed.
+    """
+    def __init__(self, out):
+        self.__out = out
+        pdb.Pdb.__init__(self)
+
+    def trace_dispatch(self, *args):
+        # Redirect stdout to the given stream.
+        save_stdout = sys.stdout
+        sys.stdout = self.__out
+        # Call Pdb's trace dispatch method.
+        try:
+            return pdb.Pdb.trace_dispatch(self, *args)
+        finally:
+            sys.stdout = save_stdout