1 files changed, 24 insertions, 0 deletions
diff --git a/astroid/helpers.py b/astroid/helpers.py
index 2b318410..feb0985e 100644
--- a/astroid/helpers.py
+++ b/astroid/helpers.py
@@ -26,6 +26,7 @@ from astroid import bases
 from astroid import context as contextmod
 from astroid import exceptions
 from astroid import manager
+from astroid import nodes
 from astroid import raw_building
 from astroid import scoped_nodes
 from astroid import util
@@ -156,3 +157,26 @@ def is_subtype(type1, type2):
 def is_supertype(type1, type2):
     """Check if *type2* is a supertype of *type1*."""
     return _type_check(type1, type2)
+
+
+def class_instance_as_index(node):
+    """Get the value as an index for the given instance.
+
+    If an instance provides an __index__ method, then it can
+    be used in some scenarios where an integer is expected,
+    for instance when multiplying or subscripting a list.
+    """
+    context = contextmod.InferenceContext()
+    context.callcontext = contextmod.CallContext(args=[node])
+
+    try:
+        for inferred in node.igetattr('__index__', context=context):
+            if not isinstance(inferred, bases.BoundMethod):
+                continue
+
+            for result in inferred.infer_call_result(node, context=context):
+                if (isinstance(result, nodes.Const)
+                        and isinstance(result.value, int)):
+                    return result
+    except exceptions.InferenceError:
+        pass