Yappi

Yet Another Python Profiler, but this time thread&coroutine&greenlet aware.

Highlights

• Fast: Yappi is fast. It is completely written in C and lots of love&care went into making it fast.
• Unique: Yappi supports multithreaded, asyncio and gevent profiling. Tagging/filtering multiple profiler results has interesting use cases.
• Intuitive: Profiler can be started/stopped and results can be obtained from any time and any thread.
• Standards Complaint: Profiler results can be saved in callgrind or pstat formats.
• Rich in Feature set: Profiler results can show either Wall Time or actual CPU Time and can be aggregated from different sessions. Various flags are defined for filtering and sorting profiler results.
• Robust: Yappi had seen years of production usage.

Motivation

CPython standard distribution comes with three deterministic profilers. cProfile, Profile and hotshot. cProfile is implemented as a C module based on lsprof, Profile is in pure Python and hotshot can be seen as a small subset of a cProfile. The major issue is that all of these profilers lack support for multi-threaded programs and CPU time.

If you want to profile a multi-threaded application, you must give an entry point to these profilers and then maybe merge the outputs. None of these profilers are designed to work on long-running multi-threaded applications. It is also not possible to profile an application that start/stop/retrieve traces on the fly with these profilers.

Now fast forwarding to 2019: With the latest improvements on asyncio library and asynchronous frameworks, most of the current profilers lacks the ability to show correct wall/cpu time or even call count information per-coroutine. Thus we need a different kind of approach to profile asynchronous code. Yappi, with v1.2 introduces the concept of coroutine profiling. With coroutine-profiling, you should be able to profile correct wall/cpu time and call count of your coroutine. (including the time spent in context switches, too). You can see details here.

Installation

Can be installed via PyPI

$ pip install yappi

OR from the source directly.

$ pip install git+https://github.com/sumerc/yappi#egg=yappi

Examples

A simple example:

import yappi

def a():
    for _ in range(10000000):  # do something CPU heavy
        pass

yappi.set_clock_type("cpu") # Use set_clock_type("wall") for wall time
yappi.start()
a()

yappi.get_func_stats().print_all()
yappi.get_thread_stats().print_all()
'''

Clock type: CPU
Ordered by: totaltime, desc

name                                  ncall  tsub      ttot      tavg      
doc.py:5 a                            1      0.117907  0.117907  0.117907

name           id     tid              ttot      scnt        
_MainThread    0      139867147315008  0.118297  1
'''

Profile a multithreaded application:

You can profile a multithreaded application via Yappi and can easily retrieve per-thread profile information by filtering on ctx_id with get_func_stats API.

import yappi
import time
import threading

_NTHREAD = 3


def _work(n):
    time.sleep(n * 0.1)


yappi.start()

threads = []
# generate _NTHREAD threads
for i in range(_NTHREAD):
    t = threading.Thread(target=_work, args=(i + 1, ))
    t.start()
    threads.append(t)
# wait all threads to finish
for t in threads:
    t.join()

yappi.stop()

# retrieve thread stats by their thread id (given by yappi)
threads = yappi.get_thread_stats()
for thread in threads:
    print(
        "Function stats for (%s) (%d)" % (thread.name, thread.id)
    )  # it is the Thread.__class__.__name__
    yappi.get_func_stats(ctx_id=thread.id).print_all()
'''
Function stats for (Thread) (3)

name                                  ncall  tsub      ttot      tavg
..hon3.7/threading.py:859 Thread.run  1      0.000017  0.000062  0.000062
doc3.py:8 _work                       1      0.000012  0.000045  0.000045

Function stats for (Thread) (2)

name                                  ncall  tsub      ttot      tavg
..hon3.7/threading.py:859 Thread.run  1      0.000017  0.000065  0.000065
doc3.py:8 _work                       1      0.000010  0.000048  0.000048


Function stats for (Thread) (1)

name                                  ncall  tsub      ttot      tavg
..hon3.7/threading.py:859 Thread.run  1      0.000010  0.000043  0.000043
doc3.py:8 _work                       1      0.000006  0.000033  0.000033
'''

Different ways to filter/sort stats:

You can use filter_callback on get_func_stats API to filter on functions, modules or whatever available in YFuncStat object.

import package_a
import yappi
import sys

def a():
    pass

def b():
    pass

yappi.start()
a()
b()
package_a.a()
yappi.stop()

# filter by module object
current_module = sys.modules[__name__]
stats = yappi.get_func_stats(
    filter_callback=lambda x: yappi.module_matches(x, [current_module])
)  # x is a yappi.YFuncStat object
stats.sort("name", "desc").print_all()
'''
Clock type: CPU
Ordered by: name, desc

name                                  ncall  tsub      ttot      tavg
doc2.py:10 b                          1      0.000001  0.000001  0.000001
doc2.py:6 a                           1      0.000001  0.000001  0.000001
'''

# filter by function object
stats = yappi.get_func_stats(
    filter_callback=lambda x: yappi.func_matches(x, [a, b])
).print_all()
'''
name                                  ncall  tsub      ttot      tavg
doc2.py:6 a                           1      0.000001  0.000001  0.000001
doc2.py:10 b                          1      0.000001  0.000001  0.000001
'''

# filter by module name
stats = yappi.get_func_stats(filter_callback=lambda x: 'package_a' in x.module
                             ).print_all()
'''
name                                  ncall  tsub      ttot      tavg
package_a/__init__.py:1 a             1      0.000001  0.000001  0.000001
'''

# filter by function name
stats = yappi.get_func_stats(filter_callback=lambda x: 'a' in x.name
                             ).print_all()
'''
name                                  ncall  tsub      ttot      tavg
doc2.py:6 a                           1      0.000001  0.000001  0.000001
package_a/__init__.py:1 a             1      0.000001  0.000001  0.000001
'''

Profile an asyncio application:

You can see that coroutine wall-time's are correctly profiled.

import asyncio
import yappi

async def foo():
    await asyncio.sleep(1.0)
    await baz()
    await asyncio.sleep(0.5)

async def bar():
    await asyncio.sleep(2.0)

async def baz():
    await asyncio.sleep(1.0)

yappi.set_clock_type("WALL")
with yappi.run():
    asyncio.run(foo())
    asyncio.run(bar())
yappi.get_func_stats().print_all()
'''
Clock type: WALL
Ordered by: totaltime, desc

name                                  ncall  tsub      ttot      tavg      
doc4.py:5 foo                         1      0.000030  2.503808  2.503808
doc4.py:11 bar                        1      0.000012  2.002492  2.002492
doc4.py:15 baz                        1      0.000013  1.001397  1.001397
'''

Profile a gevent application:

You can use yappi to profile greenlet applications now!

import yappi
from greenlet import greenlet
import time

class GreenletA(greenlet):
    def run(self):
        time.sleep(1)

yappi.set_context_backend("greenlet")
yappi.set_clock_type("wall")

yappi.start(builtins=True)
a = GreenletA()
a.switch()
yappi.stop()

yappi.get_func_stats().print_all()
'''
name                                  ncall  tsub      ttot      tavg
tests/test_random.py:6 GreenletA.run  1      0.000007  1.000494  1.000494
time.sleep                            1      1.000487  1.000487  1.000487
'''

Documentation

• Introduction

• Clock Types

• API

• Coroutine Profiling (new in 1.2)

• Greenlet Profiling (new in 1.3)

  Note: Yes. I know I should be moving docs to readthedocs.io. Stay tuned!

Related Talks

Special thanks to A.Jesse Jiryu Davis:

• Python Performance Profiling: The Guts And The Glory (PyCon 2015)

PyCharm Integration

Yappi is the default profiler in PyCharm. If you have Yappi installed, PyCharm will use it. See the official documentation for more details.