diff --git a/jedi/api.py b/jedi/api.py
index e4f7f532..4c1af950 100644
--- a/jedi/api.py
+++ b/jedi/api.py
@@ -54,13 +54,13 @@ class Script(object):
     :type source_encoding: str
     """
     def __init__(self, source, line, column, source_path,
-                                 source_encoding='utf-8'):
+                 source_encoding='utf-8', fast=True):
         api_classes._clear_caches()
         debug.reset_time()
         self.source = modules.source_to_unicode(source, source_encoding)
         self.pos = line, column
-        self._module = modules.ModuleWithCursor(source_path,
-                                        source=self.source, position=self.pos)
+        self._module = modules.ModuleWithCursor(
+            source_path, source=self.source, position=self.pos, fast=fast)
         self._source_path = source_path
         self.source_path = None if source_path is None \
                                     else os.path.abspath(source_path)
@@ -503,6 +503,59 @@ class Script(object):
         return sorted(d, key=lambda x: (x.module_path or '', x.start_pos))
 
 
+class Interpreter(Script):
+
+    """
+    Jedi API for Python REPLs.
+
+    >>> from itertools import chain
+    >>> script = Interpreter('cha', [locals()])
+    >>> script.complete()
+    [<Completion: chain>]
+
+    """
+
+    def __init__(self, source, namespaces=[], line=None, column=None,
+                 source_path=None, source_encoding='utf-8'):
+        lines = source.splitlines()
+        line = len(lines) if line is None else line
+        column = len(lines[-1]) if column is None else column
+        super(Interpreter, self).__init__(
+            source, line, column, source_path, source_encoding, fast=False)
+        for ns in namespaces:
+            self._import_raw_namespace(ns)
+
+    def _import_raw_namespace(self, raw_namespace):
+        for (variable, obj) in raw_namespace.items():
+            try:
+                module = obj.__module__
+            except:
+                continue
+            fakeimport = self._make_fakeimport(variable, module)
+            self._parser.scope.imports.append(fakeimport)
+
+    def _make_fakeimport(self, variable, module):
+        submodule = self._parser.scope._sub_module
+        varname = pr.Name(
+            module=submodule,
+            names=[(variable, (0, 0))],
+            start_pos=(0, 0),
+            end_pos=(None, None))
+        modname = pr.Name(
+            module=submodule,
+            names=[(module, (0, 0))],
+            start_pos=(0, 0),
+            end_pos=(None, None))
+        fakeimport = pr.Import(
+            module=submodule,
+            namespace=varname,
+            from_ns=modname,
+            start_pos=(0, 0),
+            end_pos=(None, None))
+        fakeimport.parent = submodule
+        return fakeimport
+
+
 def defined_names(source, source_path=None, source_encoding='utf-8'):
     """
     Get all definitions in `source` sorted by its position.
diff --git a/jedi/modules.py b/jedi/modules.py
index 37e5bbac..035a894e 100644
--- a/jedi/modules.py
+++ b/jedi/modules.py
@@ -92,8 +92,10 @@ class ModuleWithCursor(Module):
     :param position: The position, the user is currently in. Only important \
     for the main file.
     """
-    def __init__(self, path, source, position):
+    def __init__(self, path, source, position, fast):
         super(ModuleWithCursor, self).__init__(path, source)
+        self._parserclass = fast_parser.FastParser if fast else \
+                            parsing.Parser
         self.position = position
 
         # this two are only used, because there is no nonlocal in Python 2
@@ -112,7 +114,7 @@ class ModuleWithCursor(Module):
             # Call the parser already here, because it will be used anyways.
             # Also, the position is here important (which will not be used by
             # default), therefore fill the cache here.
-            self._parser = fast_parser.FastParser(self.source, self.path,
+            self._parser = self._parserclass(self.source, self.path,
                                                         self.position)
             # don't pickle that module, because it's changing fast
             cache.save_module(self.path, self.name, self._parser,