From: Tim Peters <tim.peters@gmail.com>
Date: Sun, 25 Aug 2002 17:10:17 +0000 (+0000)
Subject: Record a clue about why __or__ is not union, etc.
X-Git-Tag: v2.3c1~4299
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4924db176bdd0b4f93bf67c16487f468a1644c1c;p=python

Record a clue about why __or__ is not union, etc.
---

diff --git a/Lib/sets.py b/Lib/sets.py
index d42259108c..ff0ace0fc7 100644
--- a/Lib/sets.py
+++ b/Lib/sets.py
@@ -141,6 +141,11 @@ class BaseSet(object):
     # Standard set operations: union, intersection, both differences.
     # Each has an operator version (e.g. __or__, invoked with |) and a
     # method version (e.g. union).
+    # Subtle:  Each pair requires distinct code so that the outcome is
+    # correct when the type of other isn't suitable.  For example, if
+    # we did "union = __or__" instead, then Set().union(3) would return
+    # NotImplemented instead of raising TypeError (albeit that *why* it
+    # raises TypeError as-is is also a bit subtle).
 
     def __or__(self, other):
         """Return the union of two sets as a new set.