Zac Hatfield-Dodds
Research Scientist at Anthropic
San Francisco, California, United States
Summary
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RockstarZac Hatfield-Dodds is a research scientist and seasoned software engineer based in San Francisco with 11 years of experience improving reliability across core Python ecosystems. He’s an active open-source maintainer and PSF Fellow who blends rigorous QA and test automation with backend development—contributions span CPython, NumPy, pytest, Sphinx, Matplotlib and other high-profile projects. Zac specializes in property-based testing (Hypothesis) and doctest-driven validation, having introduced CI and fuzz-testing practices to projects like Astropy, Black, and NumPy to catch subtle, production-impacting issues. His work also touches data-science ergonomics and imaging (xarray, matplotlib) and developer tooling (flake8-bugbear, argparse/typing improvements), demonstrating attention to both user-facing behavior and developer experience. Colleagues rely on him for clear technical writing and documentation improvements that make complex features accessible and reliably testable.
11 years of coding experience
Stackoverflow
2,753reputation
52kreached
121answers
3questions
python
top-5%
Github Skills (75)
restructuredtext10
python10
testing10
guideline10
triple10
triplet10
automation10
async-await10
linter10
async10
xray10
rs10
implicit-typing10
numpy10
user-guide10
Programming languages (25)
Github contributions (5)
PyCQA/flake8-bugbear
Jan 2020 - Jan 2023
A plugin for Flake8 finding likely bugs and design problems in your program. Contains warnings that don't belong in pyflakes and pycodestyle.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:27 reviews, 12 commits, 15 PRs in 3 years
Contributions summary:Zac primarily contributed to the `flake8-bugbear` plugin, adding new checks and improving existing ones related to Python code quality. They implemented checks for exception handling, specifically addressing redundant exception types and tuple literals in `except` clauses, and also incorporated a check for late-binding loop variables. The user's work also included fixing bugs, such as those related to attribute access within `except` clauses, and adding tests to validate the changes and ensure the plugin's functionality. Furthermore, they added support for new checks and documented the changes.
linterpythonwarningspyflakesfinding
pytest-dev/pytest
May 2020 - Dec 2022
The pytest framework makes it easy to write small tests, yet scales to support complex functional testing
Role in this project:QA Engineer / Test Automation Engineer
QA Engineer / Test Automation EngineerContributions:162 reviews, 28 commits, 109 PRs in 2 years 7 months
Contributions summary:Zac primarily contributed to the testing framework of the pytest project. Their work involved modifying test files, adding new test cases, and updating existing ones to improve test coverage and functionality. They focused on testing mark registration, parametrization, and capturing output, demonstrating a strong understanding of the pytest testing framework. Furthermore, they addressed issues related to test failures, output, and code quality by improving the documentation of the testing framework.
scalespythonfunctional-testingtestingpytest-framework
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