A Python profiler that records the call stack of the executing code, instead of just the final function in it.

It uses a statistical profiler, meaning the code samples the stack periodically (every 1 ms). This is lower overhead than event- based profiling (as done by profile and cProfile).

This module is still very young, so I'd love any feedback/bug reports/pull requests!

pip install -e git+https://github.com/joerick/pyinstrument.git#egg=pyinstrument

pyinstrument supports Python 2.7 and 3.3+.

• Command-line

  You can call pyinstrument directly from the command line.

  python -m pyinstrument myscript.py [args...]
  

  This will run myscript.py to completion or until you interrupt it, and then output the call tree.

• Django

  Add pyinstrument.middleware.ProfilerMiddleware to MIDDLEWARE_CLASSES. If you want to profile your middleware as well as your view (you probably do) then put it at the start of the list.

  Then add ?profile to the end of the request URL to activate the profiler.

• Python

  from pyinstrument import Profiler
  
  profiler = Profiler() # or Profiler(use_signal=False), see below
  profiler.start()
  
  # code you want to profile
  
  profiler.stop()
  
  print(profiler.output_text(unicode=True, color=True))

  You can omit the unicode and color flags if your output/terminal does not support them.

On Mac/Linux/Unix, pyinstrument can run in 'signal' mode. This uses OS-provided signals to interrupt the process every 1ms and record the stack. It gives much lower overhead (and thus accurate) readings than the standard Python sys.setprofile style profilers. However, this can only profile the main thread.

On Windows and on multi-threaded applications, a setprofile mode is available by passing use_signal=False to the Profiler constructor. It works exactly the same as the signal mode, but has higher overhead. See the below table for an example of the amount of overhead.

                       | Django template render × 4000 | Overhead

---------------------------|------------------------------:|---------: Base | 1.46s | | | pyinstrument (signal) | 1.84s | 26% cProfile | 2.18s | 49% pyinstrument (setprofile) | 5.33s | 365% profile | 25.39s | 1739%

• When profiling Django, I'd recommend disabling django-debug-toolbar, django-devserver etc., as their instrumentation distort timings.

• In signal mode, any calls to time.sleep will return immediately. This is because of an implementation detail of time.sleep, but matches the behaviour of the C function sleep.

The standard Python profilers profile and cProfile produce output where time is totalled according to the time spent in each function. This is great, but it falls down when you profile code where most time is spent in framework code that you're not familiar with.

Here's an example of profile output when using Django.

151940 function calls (147672 primitive calls) in 1.696 seconds

   Ordered by: cumulative time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.000    0.000    1.696    1.696 profile:0(<code object <module> at 0x1053d6a30, file "./manage.py", line 2>)
        1    0.001    0.001    1.693    1.693 manage.py:2(<module>)
        1    0.000    0.000    1.586    1.586 __init__.py:394(execute_from_command_line)
        1    0.000    0.000    1.586    1.586 __init__.py:350(execute)
        1    0.000    0.000    1.142    1.142 __init__.py:254(fetch_command)
       43    0.013    0.000    1.124    0.026 __init__.py:1(<module>)
      388    0.008    0.000    1.062    0.003 re.py:226(_compile)
      158    0.005    0.000    1.048    0.007 sre_compile.py:496(compile)
        1    0.001    0.001    1.042    1.042 __init__.py:78(get_commands)
      153    0.001    0.000    1.036    0.007 re.py:188(compile)
  106/102    0.001    0.000    1.030    0.010 __init__.py:52(__getattr__)
        1    0.000    0.000    1.029    1.029 __init__.py:31(_setup)
        1    0.000    0.000    1.021    1.021 __init__.py:57(_configure_logging)
        2    0.002    0.001    1.011    0.505 log.py:1(<module>)

When you're using big frameworks like Django, it's very hard to understand how your own code relates to these traces.

Pyinstrument records the entire stack, so tracking expensive calls is much easier.