Python: Tprof, a Targeting Profiler

Summary

Python: introducing tprof, a targeting profiler2026-01-14Profilers measure the performance of a whole program to identify where most of the time is spent. But once you’ve found a target function, re-profiling the whole program to see if your changes helped can be slow and cumbersome. The profiler introduces overhead to execution and you have to pick out the stats for the one function you care about from the report. I have often gone through this loop while optimizing client or open source projects, such as when I optimized Django’s system checks framework (previous post).The pain here inspired me to create tprof, a targeting profiler for Python 3.12+ that only measures the time spent in specified target functions. Use it to measure your program before and after an optimization to see if it made any difference, with a quick report on the command line.For example, say you’ve realized that creating pathlib.Path objects is the bottleneck for your code. You could run tprof like so:Benchmark with comparison modeSometimes when optimizing code, you want to compare several functions, such as “before” and “after” versions of a function you’re optimizing. tprof supports this with its comparison mode, which adds a “delta” column to the report showing how much faster or slower each function is compared to a baseline.For example, given this code:def before(): total = 0 for i in range(100_000): total += i return total def after(): return sum(range(100_000)) for _ in range(100): before() after() …you can run tprof like this to compare the two functions:$ tprof -x -t before -t after -m example 🎯 tprof results: function calls total mean ± σ min … max delta example:before() 100 227ms 2ms ± 34μs 2ms … 2ms - example:after() 100 86ms 856μs ± 15μs 835μs … 910μs -62.27% The output shows that after() is about 60% faster than before(), in this case.Python APItprof also provides a Python API via a context manager / decorator, tprof(). Use it to profile functions within a specific block of cod...