chadwickpy

A pure-Python port of the Chadwick baseball tools: cwevent, cwgame, cwdaily, cwsub, cwcomment and cwbox. They read Retrosheet event files and write the same tables Chadwick does. No compiler, no C library, no dependencies: pip install chadwickpy.

The code is a function-by-function translation of Chadwick's C. Its output is byte-identical to the real tools on every season from 1910 to 2025 (all six tools; see Verification), apart from the differences below.

Install and use

pip install chadwickpy        # or: uv tool install chadwickpy
cwevent -y 2010 -f 0-96 2010NYA.EVA > 2010NYA.csv
cwgame -y 2010 2010NYA.EVA
chadwickpy cwbox -y 2010 2010NYA.EVA   # same tool, always this package's version
python -m chadwickpy cwdaily -y 2010 2010NYA.EVA

The command names and options are Chadwick's; see its documentation. If the C programs are also installed, whichever comes first on PATH runs; chadwickpy TOOL always runs this package. Roster (.ROS, TEAMyyyy) files are read from the event file's directory, as in Chadwick.

The library is importable too. The layout follows Chadwick's: chadwickpy (the cwlib parts: parser, game, file, roster, box score, game iterator) and chadwickpy.tools (the cwtools programs).

Speed

About 25 times slower than the C (cwevent on one team-season: 0.075 s in C, about 1.4 s here). That is the price of needing nothing but Python. Whole seasons still run in seconds to minutes.

Differences from Chadwick

• Where the C crashes or reads uninitialised memory this port raises ValueError or uses a defined value. cwbox -S (it segfaults in Chadwick 0.10.0) and the pb attribute of cwbox -X are compared against a patched build.
• The reference is Chadwick's development commit c685ab5 (it reports 0.10.0), not the released v0.10.0 tag, whose output differs on 2025 files.
• Inputs that make the C behave in undefined ways are not compared.

Verification

tests/ runs every tool against captured real-Chadwick output and, when Chadwick is available, against the real programs (set CHADWICK_BIN and CHADWICK_SRC, or build Chadwick at c685ab5; CI does). Season-sweep drivers in tests/reference/ compare whole seasons; they need the Retrosheet decade zips. Run: uv run pytest.

Licence and credit

GPL-3.0-or-later (LICENSE). This package is a derivative work of Chadwick, Copyright (C) 2002-2023 Dr T L Turocy and the Chadwick Baseball Bureau, GPL-2.0-or-later (COPYING-chadwick, NOTICE); each ported module keeps that notice. chadwickpy is independent: it is not endorsed or sponsored by Chadwick or Retrosheet, and ships no Retrosheet data.

Retrosheet's data-use notice asks that anyone using its data say so. If you publish anything built on it, include:

The information used here was obtained free of charge from and is copyrighted by Retrosheet. Interested parties may contact Retrosheet at "www.retrosheet.org".

Contributing and security

See CONTRIBUTING.md and SECURITY.md. A rule of this project: the port stays a translation of Chadwick's C. Rules are taken from the C, never guessed from output.