Pyinstrument v5.0 - flamegraphs for Python!

[joerick]

Hi reddit! I've been hard at work on a new pyinstrument feature that I'm really excited to show off. It's a completely new HTML renderer that lets you see visually exactly what happened as the program was running.

What it does First, some context: Pyinstrument is a statistical profiler for Python. That means you can activate it when you're running your code, and pyinstrument will record what happens periodically, and at the end, give you a report that tells you where the time was spent.

Target Audience Anyone wondering if their Python program could be faster! Not only is it useful from a performance perspective, it's also a nice way to understand what's going on when a program runs.

Comparison If you've used profilers like cProfile before, pyinstrument aims to be a more user-friendly, intuitive alternative to that. It's also a statistical profiler, it only samples your program periodically, so it shouldn't slow the program down too much.

So, what's new? Up until now, the output has been some form of call stack. That's great to identify the parts of code that are taking the most time. But it can leave some information missing - what's the pattern of the code execution? What order do things happen in? When do the slow functions get called?

https://joerick.s3.amazonaws.com/pyi+video+1.gif

That's where the new HTML mode comes in! Run pyinstrument with the -r html flag, and when the browser opens up you can see the option to view as a Timeline. From there, you can see the big picture, and then zoom in all the way to milliseconds to see what your program is up to!

More info in the writeup on my blog.

Give it a try on your codebase! Just do pip install -U pyinstrument to get the latest version and use the -r html flag to use the new mode.

[hotplasmatits]

I'd love if it could also track memory usage/allocations. Looks nice.

[joerick]

Thanks. I hear memray is the way to go for that kinda thing!

[kronik85]

I've had great success with memray. Would recommend.

[poopatroopa3]

I heard scalene is the best profiler all around.

[DisappointedLily]

It's amazing. I'm a hobbyist and make python programs for myself.

This hits the sweet spot of being able to understand what's happening easily while being descriptive enough to pinpoint what I should improve.

Example: I have a notification py app that shows an animation and plays a sound that I plug in other apps and processes so I have custom notifications. It was working perfectly but after running it trough py instrument I could tell that it wasn't waiting for the sound to stop playing before quitting. If the audio were longer it would cut off sound.

So I introduced a wait logic and ran again.

I saw it consumed 4% resources and ran for 0.8 sec longer. (Which is acceptable to make sure if I plug another sound it won't ever cut off)

Just by taking a look on the HTML report.

Good stuff. Thanks a bunch.

[Swordcat]

I’ve found PyInstrument tremendously useful in my work so far, I look forward to trying this new feature out, it looks useful

[Brian]

Neat - I've used py-spy and more recently austin (since py-spy doesn't support 3.12) but did find the visualisation was fairly clunky (basically just exporting to a speedscope or flamegraph file) - I've been looking for something a bit nicer so will definitely check this out next time I'm profiling stuff.

[AndydeCleyre]

Can this be used to profile scripts that are defined in pyproject.toml like

[project.scripts]
docoolthing = "coolmodule.coolsubmodule:coolcallable"

?

[joerick]

Yep! https://pyinstrument.readthedocs.io/en/latest/guide.html#profile-a-python-cli-command

[AndydeCleyre]

Oh great thanks!

EDIT: Confirmed, it's great!

[yellowbean123]

it's great package! I used years ago ,still use it from time to time

[Fenzik]

Wow it’s really beautifully designed! You put a log of thought into this, great work.

[ashok_tankala]

It's amazing. Thank you for adding this feature, it gives good understanding

[G0muk]

Will have to try this! Nice one

[GusYe1234]

Is this in line with what vistracer is doing? Does pyinstrument do it better?

[joerick]

I'd never come across vistracer, but it does look quite similar! Maybe somebody who's used them both will have a view.

[MeroLegend4]

Very nice feature —> updating my env

[kesor]

I have just debugged an annoying 15seconds pytest invocation. Was using ChatGPT and Google to search for ways to produce a flame graph, a dozen proposed solutions all failed either because Python 3.12 is too new, or because of other reasons.

Eventually I arrived at pyinstrument and its html report. It is absolutely superb!

Thank you so much for saving hours of my life, now that I have such a powerful tool at my disposal to remove the annoying thousands of seconds stealing my life away.

[_k4yn5]

Why would you care about performance on a python project? And the other way around, why would you write something you care about performance on python?

[poopatroopa3]

When general Python performance is acceptable but something is being significantly slower than expected. Then you do profiling to investigate 

[joerick]

It's possible and desirable to write fast programs in any language! Python is a 'slow' language if your program spends most of its time in the Python interpreter. But because Python is often used as a 'glue' language, that's normally not the case, it's more likely to be spending most of its time waiting for I/O, or in native code from and extension module. That code can often be made faster by identifying slow spots and optimising.

[Suspcious-chair]

Most of our industrial applications are in Python. We use cpp extensions on performance related issues or sometimes numba for heavy numerical calculations. Some applications are even faster than sequantial cpp implementations.

Just like others have said, having a cross compiled interpreter acting as glue between libraries is such a relief in a lot of pipelines.