Great question 👍. A pyproject.toml file looks intimidating at first, but it’s just a TOML-formatted config. The trick is to know the sections that matter.
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How to Read a pyproject.toml
- Build system
[build-system] requires = ["setuptools>=61.0"] build-backend = "setuptools.build_meta"
• requires → which packages are needed to build (not run) the project.
• build-backend → tells Python which tool builds the wheel (setuptools, poetry.core, hatchling, etc.).👉 This tells you what ecosystem you’re in (setuptools vs Poetry vs Hatch).
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- Project metadata
[project] name = "mypackage" version = "0.1.0" description = "Example project" authors = [{name="Alice", email="[email protected]"}] dependencies = ["requests>=2.0", "numpy"]
• name / version → how PyPI will see the package.
• description → human-readable summary.
• authors → credits.
• dependencies → runtime dependencies installed with pip install mypackage.👉 Read this section to know what the package is and what it needs.
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- Optional / extra dependencies
[project.optional-dependencies] dev = ["pytest", "black"] docs = ["sphinx"]
• These are extras, installed with pip install mypackage[dev].👉 Lets you see what’s needed for dev vs docs vs testing.
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- Tool-specific sections
[tool.black] line-length = 88
[tool.pytest.ini_options] testpaths = ["tests"]
• Each tool (Black, Ruff, Mypy, Pytest) puts its config under tool.<name>.👉 This replaces having separate files like .flake8 or pytest.ini.
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- Other sections you might see • [tool.poetry] → if Poetry is managing the whole project. • [tool.hatch] → if Hatch is used. • [tool.setuptools] → setuptools extra configs. • [tool.coverage] → test coverage rules.
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How to actually read it
When you open a pyproject.toml, skim in this order: 1. [build-system] → which ecosystem? (Poetry, setuptools, Hatch). 2. [project] → package metadata and core dependencies. 3. [project.optional-dependencies] → extras for dev/docs/tests. 4. [tool.*] → configs for code quality and testing tools.
That’s 90% of what matters.
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✅ Pro tip: It’s like package.json in Node.js. Once you know which backend you’re in, the rest falls into place.
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Would you like me to take the pyproject.toml from your screenshot/repo and walk you through it line by line? That way you’ll see these concepts directly in action.