about things
clarify dependency groups vs optional dependencies
groups (PEP 735) stay local, optional deps go into package metadata
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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languages/python/ecosystem/project-setup.md
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languages/python/ecosystem/project-setup.md
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key patterns:
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- `dynamic = ["version"]` - version comes from git tags, not manual editing
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- `[dependency-groups]` - dev deps separate from runtime deps
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- `[project.scripts]` - CLI entry points
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## dependency groups vs optional dependencies
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these look similar but serve different purposes.
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**dependency groups** (PEP 735) are local-only. they never appear in published package metadata. users who `pip install` your package won't see them:
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```toml
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[dependency-groups]
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dev = ["pytest", "ruff"]
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docs = ["mkdocs", "mkdocs-material"]
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```
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install with `uv sync --group dev`. CI can install only what it needs.
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**optional dependencies** are published in package metadata. users can install them:
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```toml
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[project.optional-dependencies]
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aws = ["prefect-aws"]
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mcp = ["fastmcp>=2.0"]
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```
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install with `pip install mypackage[aws]` or `uv add 'mypackage[mcp]'`.
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use groups for dev/test/CI. use optional deps for features consumers might want.
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from [switching a big python library from setup.py to pyproject.toml](https://blog.zzstoatzz.io/switching-a-big-python-library-from-setuppy-to-pyprojecttoml/)
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## versioning from git tags
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myproject = "myproject.cli:main"
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myproject-mcp = "myproject.mcp:main"
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```
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## optional dependencies
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for features that not everyone needs:
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```toml
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[project.optional-dependencies]
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mcp = ["fastmcp>=2.0"]
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```
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install with `uv sync --extra mcp` or `uv add 'myproject[mcp]'`.
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## uv workspaces
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