> On 14 Feb 2017, at 17:39, Kyle Lahnakoski <klahnako...@mozilla.com> wrote: > > > Can you wrap the expensive functions in lambdas? And have your logger > evaluate it, only if required? > >> debugLog( ‘info is %r’ % (lambda: expensiveFunction(),) )
Interesting idea. I will bench mark and see what the cost of the lamba version is. It would still be nice to have the code look cleaner without the lambda. Barry > > >> On 2017-02-14 10:51, Barry Scott wrote: >> A common pattern I use is to have logging calls for debug and information >> with my applications. >> The logging calls can be separately enabled and disabled. >> >> For example: >> >> debug_log_enabled = False >> def debugLog( msg ): >> If debug_log_enabled: >> print( ‘Debug: %s’ % (msg,) ) >> >> Then the caller can simple write: >> >> def main(): >> debugLog( ‘Start of main’ ) >> >> This is fine until the evaluation of the msg becomes expensive. >> >> debugLog( ‘info is %r’ % (expensiveFunction(),) ) >> >> What would be nice is to be able to avoid evaluation the tuple of arguments >> if debug is >> disabled as this can be expensive. I can write this: >> >> if debug_log_enabled: debugLog( ‘info is %r’ % (expensiveFunction(),) ) >> >> But that is a more code then I would like to write. And if the debug code is >> a performance problem cannot >> be left in the production code. >> >> I could combine the boolean and the log function by using a class to tidy up >> the implementation. >> >> class DebugLog: >> def __init__( self, enabled = False ): >> self.enabled = enabled >> >> def __bool__( self ): >> return self.enabled >> >> def __call__( self, msg ): >> if self.enabled: print( ‘Debug: %s’ % (msg,) ) >> >> And call like this: >> >> dbg_log = DebugLog() >> >> If dbg_log: dbg_log( ‘a debug message’ ) >> >> But I’d like to only write: >> >> dbg_log( ‘a debug message’ ) >> >> And have the evaluation of the argument skipped unless its dbg_log is >> enabled. >> >> I cannot see how to do this with python as it stands. >> >> Something would have to be added to allow python to short circuit the >> argument tuple evaluation. >> >> Maybe python can check for a special dunder on the class that know how to do >> this idiom, __if_true_call__? >> >> Thoughts? >> >> Barry >> >> _______________________________________________ >> Python-ideas mailing list >> Python-ideas@python.org >> https://mail.python.org/mailman/listinfo/python-ideas >> Code of Conduct: http://python.org/psf/codeofconduct/ > > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ _______________________________________________ Python-ideas mailing list Python-ideas@python.org https://mail.python.org/mailman/listinfo/python-ideas Code of Conduct: http://python.org/psf/codeofconduct/
