[Python-checkins] r54977 - peps/trunk/pep-3119.txt

[guido.van.rossum]

Author: guido.van.rossum
Date: Thu Apr 26 02:44:37 2007
New Revision: 54977

Modified:
   peps/trunk/pep-3119.txt
Log:
Make clear() a concrete method that calls pop() until it raises KeyError.


Modified: peps/trunk/pep-3119.txt
==============================================================================
--- peps/trunk/pep-3119.txt	(original)
+++ peps/trunk/pep-3119.txt	Thu Apr 26 02:44:37 2007
@@ -407,14 +407,6 @@
         was present and ``False`` if it wasn't.  The abstract
         implementation raises ``NotImplementedError``.
 
-    ``.clear()``
-        Abstract method that empties the set.  The abstract
-        implementation raises ``NotImplementedError``.  (Making this
-        concrete would just add a slow, cumbersome default
-        implementation.)  **Open issues:** Forcing every mutable set
-        to implement this may be a pain for such a fairly
-        non-essential method.  Perhaps just drop it?
-
     ``.pop()``
         Concrete method that removes an arbitrary item.  If the set is
         empty, it raises ``KeyError``.  The default implementation
@@ -426,6 +418,14 @@
         return ``True`` if ``x`` was added, ``False`` if it was
         removed.
 
+    ``.clear()``
+        Concrete method that empties the set.  The default
+        implementation repeatedly calls ``self.pop()`` until
+        ``KeyError`` is caught.  (Note: this is probably much slower
+        than simply creating a new set, even if an implementation
+        overrides it with a faster approach; but in some cases object
+        identity is important.)
+
     This also supports the in-place mutating operations ``|=``,
     ``&=``, ``^=``, ``-=``.  These are concrete methods whose right
     operand can be an arbitrary ``Iterable``, except for ``&=``, whose
@@ -491,8 +491,8 @@
 ``MutableMapping``
     A subclass of ``Mapping`` that also implements some standard
     mutating methods.  Abstract methods include ``__setitem__``,
-    ``__delitem__``, ``clear``, ``update``.  Concrete methods include
-    ``pop``, ``popitem``.  Note: ``setdefault`` is *not* included.
+    ``__delitem__``.  Concrete methods include ``pop``, ``popitem``,
+    ``clear``, ``update``.  Note: ``setdefault`` is *not* included.
 
 **Open issues:**