http://code.activestate.com/recipes/users/4182937/2012-08-22T17:57:12-07:00ActiveState Code Recipes2012-08-22T17:57:12-07:00Cyrilhttp://code.activestate.com/recipes/users/4182937/http://code.activestate.com/recipes/578221-recipe-with-no-name-yet/

<p style="color: grey"> Python recipe 578221 by <a href="/recipes/users/4182937/">Cyril</a> (<a href="/recipes/tags/check/">check</a>, <a href="/recipes/tags/debug/">debug</a>, <a href="/recipes/tags/decorator/">decorator</a>, <a href="/recipes/tags/wrapper/">wrapper</a>). Revision 9. </p> <p>Not a very new recipe, but a short one and (I hope) useful :</p> <ul> <li>wrapping any function "f" with two decorators "enter_event" and "exit_event" that will trigger calling of user functions when, ... hum ... evidently, <strong>just before entering and just after exiting the "f" function</strong>.</li> </ul> <p>Typical usages :</p> <ul> <li>debugging on a function by function basis : <ul> <li>emit a trace in log file to see when functions are called and check sequences correctness (very usefull when programming by events)</li> <li>feed a profile analyzer (by fine tuning which functions are enabled)</li> <li>feed a code coverage analyzer ( " )</li> </ul></li> <li>kind of validator on function calling : <ul> <li>implement programming by contracts : <ul> <li>check that parameters values of "f" function will not have an unexpected value or be of an unexpected type</li> <li>this allow to increase code robustness by narrowing </li> </ul></li> <li>implement invariants (eg. check that returned value is always in the excepted range, ...)</li> <li>insure that a function follow specifications by meta-checking that has always predictable results (eg. return the fixed expected value for each possible input value, ...)</li> </ul></li> <li>minimum modification of existing code</li> <li><strong>in the same thinking line as the "monkey patching" concept</strong></li> </ul> <p>Notes on usage :</p> <ul> <li>recipe works on functions and any kind of methods (methods, class methods, and static methods)</li> <li>the usage order of "@enter_event" and "@exit_event" decorators doesn't matter : the result will be the same</li> </ul> <ul> <li><em>PLEASE VOTE FOR THIS RECIPE if you like it !</em></li> </ul>