[Python-checkins] python/nondist/peps pep-0343.txt,1.20,1.21

[gvanrossum@users.sourceforge.net]

Update of /cvsroot/python/python/nondist/peps
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv22249

Modified Files:
	pep-0343.txt 
Log Message:
Include suggestions from Nick Coghlan.


Index: pep-0343.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0343.txt,v
retrieving revision 1.20
retrieving revision 1.21
diff -u -d -r1.20 -r1.21
--- pep-0343.txt	2 Jun 2005 14:56:36 -0000	1.20
+++ pep-0343.txt	2 Jun 2005 15:13:55 -0000	1.21
@@ -413,7 +413,9 @@
     which does not do what one might think (f is closed before BLOCK2
     is entered).
 
-    OTOH such mistakes are easily diagnosed.
+    OTOH such mistakes are easily diagnosed; for example, the
+    with_template decorator above raises RuntimeError when the second
+    with-statement calls f.__enter__() again.
 
 Open Issues
 
@@ -642,6 +644,29 @@
        methods to the decimal.Context class so that this example can
        be simplified to "with decimal.getcontext() as ctx: ...".)
 
+    10. A generic "object-closing" template:
+
+        @with_template
+        def closing(obj):
+            try:
+                yield obj
+            finally:
+                obj.close()
+
+        This can be used to deterministically close anything with a
+        close method, be it file, generator, or something else:
+
+        # emulate opening():
+        with closing(open("argument.txt")) as contradiction:
+           for line in contradiction:
+               print line
+
+        # deterministically finalize a generator:
+        with closing(some_gen()) as data:
+           for datum in data:
+               process(datum)
+
+
 References
 
     [1] http://blogs.msdn.com/oldnewthing/archive/2005/01/06/347666.aspx