Index: Lib/inspect.py
===================================================================
--- Lib/inspect.py	(revision 80573)
+++ Lib/inspect.py	(working copy)
@@ -434,8 +434,10 @@
     info = getmoduleinfo(path)
     if info: return info[0]
 
-def getsourcefile(object):
-    """Return the Python source file an object was defined in, if it exists."""
+def getsourcefile(object, check=True):
+    """Return the Python source filename an object was defined in or None
+    if ``check`` is true (the default) and the filename does not exist 
+    and was not created by a PEP 302 loader."""
     filename = getfile(object)
     if filename[-4:].lower() in ('.pyc', '.pyo'):
         filename = filename[:-4] + '.py'
@@ -443,6 +445,8 @@
         if 'b' in mode and filename[-len(suffix):].lower() == suffix:
             # Looks like a binary file.  We want to only return a text file.
             return None
+    if not check:
+        return filename
     if os.path.exists(filename):
         return filename
     # only return a non-existent filename if the module has a PEP 302 loader
@@ -514,9 +518,7 @@
     or code object.  The source code is returned as a list of all the lines
     in the file and the line number indexes a line in that list.  An IOError
     is raised if the source code cannot be retrieved."""
-    file = getsourcefile(object)
-    if not file:
-        raise IOError('source code not available')
+    file = getsourcefile(object, check=False)
     module = getmodule(object, file)
     if module:
         lines = linecache.getlines(file, module.__dict__)
Index: Lib/test/test_inspect.py
===================================================================
--- Lib/test/test_inspect.py	(revision 80573)
+++ Lib/test/test_inspect.py	(working copy)
@@ -2,6 +2,7 @@
 import types
 import unittest
 import inspect
+import linecache
 import datetime
 import collections
 from os.path import normcase
@@ -250,6 +251,10 @@
     def test_getsourcefile(self):
         self.assertEqual(normcase(inspect.getsourcefile(mod.spam)), modfile)
         self.assertEqual(normcase(inspect.getsourcefile(git.abuse)), modfile)
+        fn = "_non_existing_filename_used_for_sourcefile_test.py"
+        co = compile("None", fn, "exec")
+        self.assertEqual(normcase(inspect.getsourcefile(co, check=False)), fn)
+        self.assertEqual(normcase(inspect.getsourcefile(co, check=True)), None)
 
     def test_getfile(self):
         self.assertEqual(inspect.getfile(mod.StupidGit), mod.__file__)
@@ -348,6 +353,15 @@
         self.assertRaises(IOError, inspect.getsource, unicodedata)
         self.assertRaises(IOError, inspect.findsource, unicodedata)
 
+    def test_findsource_code_in_linecache(self):
+        lines = ["x=1"]
+        co = compile(lines[0], "_dynamically_created_file", "exec")
+        self.assertRaises(IOError, inspect.findsource, co)
+        self.assertRaises(IOError, inspect.getsource, co)
+        linecache.cache[co.co_filename] = (1, None, lines, co.co_filename)
+        self.assertEquals(inspect.findsource(co), (lines,0))
+        self.assertEquals(inspect.getsource(co), lines[0])
+
 # Helper for testing classify_class_attrs.
 def attrs_wo_objs(cls):
     return [t[:3] for t in inspect.classify_class_attrs(cls)]