10.8 Extensions -- Deriving Better Profilers

The Profile class of module profile was written so that derived classes could be developed to extend the profiler. Rather than describing all the details of such an effort, I'll just present the following two examples of derived classes that can be used to do profiling. If the reader is an avid Python programmer, then it should be possible to use these as a model and create similar (and perchance better) profile classes.

If all you want to do is change how the timer is called, or which timer function is used, then the basic class has an option for that in the constructor for the class. Consider passing the name of a function to call into the constructor:

pr = profile.Profile(your_time_func)

The resulting profiler will call your_time_func() instead of os.times(). The function should return either a single number or a list of numbers (like what os.times() returns). If the function returns a single time number, or the list of returned numbers has length 2, then you will get an especially fast version of the dispatch routine.

Be warned that you should calibrate the profiler class for the timer function that you choose. For most machines, a timer that returns a lone integer value will provide the best results in terms of low overhead during profiling. (os.times() is pretty bad, 'cause it returns a tuple of floating point values, so all arithmetic is floating point in the profiler!). If you want to substitute a better timer in the cleanest fashion, you should derive a class, and simply put in the replacement dispatch method that better handles your timer call, along with the appropriate calibration constant :-).


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