[Python-Dev] maximum recursion depth exceeded in lib\pstats.py

[Michael Foord]

  On 21/10/2010 12:20, Adam Bielański wrote:
>  Hi all,
>
> There's a bug in Python 2.6, module lib\pstats.py, line 150. I'm 
> pretty sure, however that it also exists in other versions, as I don't 
> think that profiler differs very much between them.
>
> Let me paste a little piece of surrounding code:
>
>     class Stats:
>       (....)
>         def add(self, *arg_list):
>             if not arg_list: return self
>             if len(arg_list) > 1: self.add(*arg_list[1:])  #Line 150, 
> the problem is right here!
>             other = arg_list[0]
>             (... do some processing with first item from arg_list ...)
>
> This is the code for adding profiling stats from multiple files (names 
> are on arg_list) so that they can be displayed in cumulated and 
> readable form.
>
> As you can see it chops off the first item from the list and then uses 
> recursion to process the rest of it. It's no wonder then that when you 
> profiled a little too many function calls, you're bound to see 
> RuntimeError with 'maximum recursion depth exceeded' message when you 
> try using this. IMO this should be done with iteration instead, like:
>
>         def add(self, *arg_list):
>             if not arg_list: return self
>             for other in arg_list: #Preserved variable name only for 
> sake of comparison with previous snippet
>                 (... do some processing with each item from arg_list, 
> merging results in some rightful manner ...)
>

Without looking at the details your diagnosis and suggested fix seem good.

Please raise an issue on the Python bug tracker - preferably with patch 
and test.

http://bugs.python.org/

All the best,

Michael Foord


>
> Kind regards,
>     Adam Bielanski.
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