[Python-ideas] Allow Profile() to be used as a context manager

[David Townshend]

shameless-advertisement noted!  It looks like a useful tool, but I had
something rather simpler in mind, and something included in the stdlib.  I
think adding a decorator too is a good idea, but as pointed out there is
already a patch for this.

David

On Wed, Jan 25, 2012 at 1:37 PM, Robert Kern <robert.kern at gmail.com> wrote:

> On 1/25/12 8:19 AM, Yuval Greenfield wrote:
>
>> On Wed, Jan 25, 2012 at 8:36 AM, David Townshend
>> <aquavitae69 at gmail.com
>> <mailto:aquavitae69 at gmail.com>**> wrote:
>>
>>    [...]
>>    Any major objections to this?
>>
>>
>>
>>  At first this sounded like a good idea but 2 things pop to mind:
>>
>>  1. How does one get the pstat profiling output from the context manager?
>> Will
>>
>>    printing out the results be the only option?
>>  2. Usually when I profile I don't want to touch the code at all so
>> eventually
>>
>>    if I'll use this context manager it'll be more akin to
>>
>>
>>     with profile.Profiler():
>>         main()
>>
>> Which isn't much of a win over
>>
>>     profile.run('main()')
>>
>>
>> Now if you're talking about a reentrant profiler, that's interesting:
>>
>>     profiler = profile.Profiler()
>>
>>     while is_working:
>>         with profiler:
>>             do_hard_task()
>>     do_a_hard_but_i_dont_care_now_**task()
>>
>>     with profiler:
>>         do_a_diff_hard_task()
>>
>>
>> and then I can call whatever method is there to get the pstat. If this is
>> the
>> vision then it sounds awesome.
>>
>
> <shameless-advertisement>
>
> You may want to take a look at my kernprof script mentioned elsewhere in
> the thread:
>
>  http://packages.python.org/**line_profiler/<http://packages.python.org/line_profiler/>
>  http://pypi.python.org/pypi/**line_profiler/<http://pypi.python.org/pypi/line_profiler/>
>
> Besides adding the context manager to Profile, it is a generic "runner"
> script that will run your script under the profiler and dump the results to
> a file. In the normal use case of profiling the entire script, you don't
> have to modify your code at all:
>
>  [line_profiler]$ kernprof.py -v pystone.py
>  Pystone(1.1) time for 50000 passes = 0.918603
>  This machine benchmarks at 54430.5 pystones/second
>  Wrote profile results to pystone.py.prof
>           1100070 function calls in 0.929 seconds
>
>     Ordered by: standard name
>
>     ncalls  tottime  percall  cumtime  percall filename:lineno(function)
>          1    0.000    0.000    0.929    0.929 <string>:1(<module>)
>      50000    0.140    0.000    0.322    0.000 pystone.py:137(Proc1)
>      50000    0.029    0.000    0.029    0.000 pystone.py:153(Proc2)
>      50000    0.036    0.000    0.048    0.000 pystone.py:164(Proc3)
>      50000    0.015    0.000    0.015    0.000 pystone.py:174(Proc4)
>      50000    0.013    0.000    0.013    0.000 pystone.py:181(Proc5)
>      50000    0.033    0.000    0.043    0.000 pystone.py:188(Proc6)
>     150000    0.034    0.000    0.034    0.000 pystone.py:207(Proc7)
>      50000    0.100    0.000    0.126    0.000 pystone.py:212(Proc8)
>     150000    0.035    0.000    0.035    0.000 pystone.py:225(Func1)
>  ...
>
> But if you do want to use the context manager or the decorator, then there
> is a flag to the script that injects the Profile instance into the
> builtins. Then you can use "@profile" or "with profile:" to only enable the
> profiler at certain points (and multiple points as in your use case above).
> These are the only modifications you need to make. The stats dumping is
> handled by kernprof.
>
>  [line_profiler]$ grin -A10 '@profile' pystone.py
>  pystone.py:
>    164 : @profile
>    165 + def Proc3(PtrParOut):
>    166 +     global IntGlob
>    167 +
>    168 +     if PtrGlb is not None:
>    169 +         PtrParOut = PtrGlb.PtrComp
>    170 +     else:
>    171 +         IntGlob = 100
>    172 +     PtrGlb.IntComp = Proc7(10, IntGlob)
>    173 +     return PtrParOut
>    174 +
>    182 : @profile
>    183 + def Proc5():
>    184 +     global Char1Glob
>    185 +     global BoolGlob
>    186 +
>    187 +     Char1Glob = 'A'
>    188 +     BoolGlob = FALSE
>    189 +
>    190 + def Proc6(EnumParIn):
>    191 +     EnumParOut = EnumParIn
>    192 +     if not Func3(EnumParIn):
>
>  [line_profiler]$ kernprof.py -v --builtin pystone.py
>  Pystone(1.1) time for 50000 passes = 1.08921
>  This machine benchmarks at 45904.8 pystones/second
>  Wrote profile results to pystone.py.prof
>           350000 function calls in 0.192 seconds
>
>     Ordered by: standard name
>
>     ncalls  tottime  percall  cumtime  percall filename:lineno(function)
>     100000    0.116    0.000    0.123    0.000 kernprof.py:73(disable_by_*
> *count)
>      50000    0.042    0.000    0.055    0.000 pystone.py:164(Proc3)
>      50000    0.013    0.000    0.013    0.000 pystone.py:182(Proc5)
>      50000    0.013    0.000    0.013    0.000 pystone.py:209(Proc7)
>     100000    0.007    0.000    0.007    0.000 {method 'disable' of
> '_lsprof.Profiler' objects}
>
> </shameless-advertisement>
>
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless
> enigma
>  that is made terrible by our own mad attempt to interpret it as though it
> had
>  an underlying truth."
>  -- Umberto Eco
>
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