From: Raymond Hettinger <python@rcn.com>
Date: Thu, 16 Dec 2010 02:24:12 +0000 (+0000)
Subject: Improve the ContextDecorator example.
X-Git-Tag: v3.2b2~57
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=9743e4f6169b3abe8cde3fc4cae1d7b673e29d6d;p=python

Improve the ContextDecorator example.
---

diff --git a/Doc/whatsnew/3.2.rst b/Doc/whatsnew/3.2.rst
index 31f57e1c2b..cc5ea4989c 100644
--- a/Doc/whatsnew/3.2.rst
+++ b/Doc/whatsnew/3.2.rst
@@ -818,33 +818,31 @@ definition:
 >>> import logging
 >>> logging.basicConfig(level=logging.INFO)
 >>> @contextmanager
-... def track_entry_and_exit():
-...     logging.info('Entry')
+... def track_entry_and_exit(name):
+...     logging.info('Entering: {}'.format(name))
 ...     yield
-...     logging.info('Exit')
+...     logging.info('Exiting: {}'.format(name))
 
 Formerly, this would have only been usable as a context manager:
 
->>> with track_entry_and_exit():
+>>> with track_entry_and_exit('widget loader'):
 ...     print('Some time consuming activity goes here')
+...     load_widget()
 
 Now, it can be used as a decorator as well:
 
->>> @track_entry_and_exit
+>>> @track_entry_and_exit('widget loader')
 ... def activity():
-...     print('Some time consuming activity goes here'
+...     print('Some time consuming activity goes here')
+...     load_widget()
 
 Trying to fulfill two roles at once places some limitations on the technique.
 Context managers normally have the flexibility to return an argument usable by
-the :keyword:`with`-statement, and function decorators can be constructed to
-accept arguments or to know the name of the function they are enclosing.  Since
-those features of context managers and function decorators are not overlapping,
-those features are not supported.
-
-In the above example, there is not a clean way for the
-:func:`track_entry_and_exit` decorator to know the name of the enclosed
-function.  Likewise, the *track_entry_and_exit* context manager does not have a
-way to return a logging instance for use in the body of enclosed statements.
+the :keyword:`with`-statement, but there is no parallel for function decorators.
+
+In the above example, there is not a clean way for the *track_entry_and_exit*
+context manager does not have a way to return a logging instance for use in the
+body of enclosed statements.
 
 (Contributed by Michael Foord in :issue:`9110`.)