`_colorize` module is slow to import, affecting `traceback` and `logging` modules

“It is a truth universally acknowledged, that a module in possession of great colors, suffers import time slowdown.

_colorize module is slow to import due to its use of dataclasses

python -Ximporttime -c "import _colorize"

Visualization in tuna

Notice that significant time is also spent executing the _colorize, due to the creation of its dataclasses

❯ uvx python@3.15 -m cProfile -m _colorize | head -15
         5609 function calls (5489 primitive calls) in 0.006 seconds

   Ordered by: cumulative time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
      9/1    0.003    0.000    0.006    0.006 {built-in method builtins.exec}
        1    0.000    0.000    0.006    0.006 <string>:1(<module>)
        1    0.000    0.000    0.006    0.006 <frozen runpy>:199(run_module)
        1    0.000    0.000    0.006    0.006 <frozen runpy>:65(_run_code)
        1    0.000    0.000    0.006    0.006 _colorize.py:1(<module>)
        7    0.000    0.000    0.005    0.001 dataclasses.py:1432(wrap)
        7    0.000    0.000    0.005    0.001 dataclasses.py:986(_process_class)
        7    0.000    0.000    0.003    0.000 dataclasses.py:478(add_fns_to_class)
        4    0.000    0.000    0.001    0.000 inspect.py:3342(signature)
        4    0.000    0.000    0.001    0.000 inspect.py:3055(from_callable)

The slow import time directly affects (among others) the traceback module which in turn affects logging, which is 40% slower in 3.14 and 3.15 compared to 3.13. That is quite unfortunate since in applications that care about import time, logging module is typically hard to avoid (I originally discovered this when looking at pip's startup time)

 hyperfine -w 10 "python3.13 -c 'import logging'"  "python3.15 -c 'import logging'" 
Benchmark 1: python3.13 -c 'import logging'
  Time (mean ± σ):      21.0 ms ±   3.4 ms    [User: 14.8 ms, System: 5.9 ms]
  Range (min … max):    16.2 ms …  28.2 ms    155 runs
 
Benchmark 2: python3.15 -c 'import logging'
  Time (mean ± σ):      29.6 ms ±   2.1 ms    [User: 22.2 ms, System: 7.0 ms]
  Range (min … max):    26.4 ms …  35.1 ms    100 runs
 
Summary
  python3.13 -c 'import logging' ran
    1.40 ± 0.25 times faster than /home/hollas/.local/share/uv/python/cpython-3.15.0a5-linux-x86_64-gnu/bin/python3.15 -c 'import logging'

It's not very clear how to make this better (besides not using dataclasses). We tried to make traceback lazy in logging, but failed. #112995

Linked PRs

• gh-144879
• gh-149318

Start with the _colorize module and reproduce its import profile using python -Ximporttime -c "import _colorize" and the cProfile command shown. Compare the logging benchmarks, then review linked PRs gh-144879 and gh-149318; done means reducing the import overhead affecting _colorize, traceback, and logging.