From 4cd7abaa350cc7b465b90a26e87f5c73e32a2d1f Mon Sep 17 00:00:00 2001
From: Zhongyue Luo <zhongyue.nah@intel.com>
Date: Thu, 31 Jan 2013 14:23:27 +0800
Subject: Fixes 'not in' operator usage

Change-Id: I50a5bbe4800fc88b631701a6be0a0f9feec597d0
---
 HACKING.rst | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'HACKING.rst')

diff --git a/HACKING.rst b/HACKING.rst
index cf6abb39..bf0befca 100644
--- a/HACKING.rst
+++ b/HACKING.rst
@@ -18,6 +18,24 @@ General
 - Do not name anything the same name as a built-in or reserved word
 - When defining global constants, define them before functions and classes
 - Avoid using "double quotes" where you can reasonably use 'single quotes'
+- Use the "is not" operator when testing for unequal identities. Example::
+
+    if not X is Y:  # BAD, intended behavior is ambiguous
+        pass
+
+    if X is not Y:  # OKAY, intuitive
+        pass
+
+- Use the "not in" operator for evaluating membership in a collection. Example::
+
+    if not X in Y:  # BAD, intended behavior is ambiguous
+        pass
+
+    if X not in Y:  # OKAY, intuitive
+        pass
+
+    if not (X in Y or X in Z):  # OKAY, still better than all those 'not's
+        pass
 
 
 TODO vs FIXME
-- 
cgit