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Specifying dependencies#

In uv, project dependencies are declared across two pyproject.toml tables: project.dependencies and tool.uv.sources.

project.dependencies defines the standards-compliant dependency metadata, propagated when uploading to PyPI or building a wheel.

tool.uv.sources enriches the dependency metadata with additional sources, incorporated during development. A dependency source can be a Git repository, a URL, a local path, or an alternative registry.

tool.uv.sources enables uv to support common patterns like editable installations and relative paths that are not supported by the project.dependencies standard. For example:

pyproject.toml
[project]
name = "albatross"
version = "0.1.0"
dependencies = [
  "bird-feeder",
]

[tool.uv.sources]
bird-feeder = { path = "./packages/bird-feeder" }

Project dependencies#

The project.dependencies table represents the dependencies that are used when uploading to PyPI or building a wheel. Individual dependencies are specified using PEP 508 syntax, and the table follows the PEP 621 standard.

project.dependencies defines the list of packages that are required for the project, along with the version constraints that should be used when installing them. Each entry includes a dependency name and version. An entry may include extras or environment markers for platform-specific packages. For example:

pyproject.toml
[project]
name = "albatross"
version = "0.1.0"
dependencies = [
  # Any version in this range
  "tqdm >=4.66.2,<5",
  # Exactly this version of torch
  "torch ==2.2.2",
  # Install transformers with the torch extra
  "transformers[torch] >=4.39.3,<5",
  # Only install this package on older python versions
  # See "Environment Markers" for more information
  "importlib_metadata >=7.1.0,<8; python_version < '3.10'",
  "mollymawk ==0.1.0"
]

If the project only requires packages from standard package indexes, then project.dependencies is sufficient. If the project depends on packages from Git, remote URLs, or local sources, tool.uv.sources can be used to enrich the dependency metadata without ejecting from the stands-compliant project.dependencies table.

Tip

See the projects documentation to add, remove, or update dependencies from the pyproject.toml from the CLI.

Dependency sources#

During development, a project may rely on a package that isn't available on PyPI. The following additional sources are supported by uv:

  • Git: A Git repository.
  • URL: A remote wheel or source distribution.
  • Path: A local wheel, source distribution, or project directory.
  • Workspace: A member of the current workspace.

Only a single source may be defined for each dependency.

Note that if a non-uv project uses a project with sources as a Git- or path-dependency, only project.dependencies and project.optional-dependencies are respected. Any information provided in the source table will need to be re-specified in a format specific to the other package manager.

To instruct uv to ignore the tool.uv.sources table (e.g., to simulate resolving with the package's published metadata), use the --no-sources flag:

$ uv lock --no-sources

The use of --no-sources will also prevent uv from discovering any workspace members that could satisfy a given dependency.

Git#

To add a Git dependency source, prefix a Git-compatible URL to clone with git+.

For example:

$ uv add git+https://github.com/encode/httpx

Will result in a pyproject.toml with:

pyproject.toml
[project]
dependencies = [
    "httpx",
]

[tool.uv.sources]
httpx = { git = "https://github.com/encode/httpx" }

A revision, tag, or branch may also be included:

$ uv add git+https://github.com/encode/httpx --tag 0.27.0
$ uv add git+https://github.com/encode/httpx --branch main
$ uv add git+https://github.com/encode/httpx --rev 326b943

Git dependencies can also be manually added or edited in the pyproject.toml with the { git = <url> } syntax. A target revision may be specified with one of: rev, tag, or branch. A subdirectory may be specified if the package isn't in the repository root.

URL#

To add a URL source, provide a https:// URL to either a wheel (ending in .whl) or a source distribution (typically ending in .tar.gz or .zip; see here for all supported formats).

For example:

$ uv add "https://files.pythonhosted.org/packages/5c/2d/3da5bdf4408b8b2800061c339f240c1802f2e82d55e50bd39c5a881f47f0/httpx-0.27.0.tar.gz"

Will result in a pyproject.toml with:

pyproject.toml
[project]
dependencies = [
    "httpx",
]

[tool.uv.sources]
httpx = { url = "https://files.pythonhosted.org/packages/5c/2d/3da5bdf4408b8b2800061c339f240c1802f2e82d55e50bd39c5a881f47f0/httpx-0.27.0.tar.gz" }

URL dependencies can also be manually added or edited in the pyproject.toml with the { url = <url> } syntax. A subdirectory may be specified if the source distribution isn't in the archive root.

Path#

To add a path source, provide the path of a wheel (ending in .whl), a source distribution (typically ending in .tar.gz or .zip; see here for all supported formats), or a directory containing a pyproject.toml.

For example:

$ uv add /example/foo-0.1.0-py3-none-any.whl

Will result in a pyproject.toml with:

pyproject.toml
[project]
dependencies = [
    "foo",
]

[tool.uv.sources]
foo = { path = "/example/foo-0.1.0-py3-none-any.whl" }

The path may also be a relative path:

$ uv add ./foo-0.1.0-py3-none-any.whl

Or, a path to a project directory:

$ uv add ~/projects/bar/

Important

An editable installation is not used for path dependencies by default. An editable installation may be requested for project directories:

$ uv add --editable ~/projects/bar/

However, it is recommended to use workspaces instead of manual path dependencies.

Workspace member#

To declare a dependency on a workspace member, add the member name with { workspace = true }. All workspace members must be explicitly stated. Workspace members are always editable . See the workspace documentation for more details on workspaces.

pyproject.toml
[project]
dependencies = [
  "mollymawk ==0.1.0"
]

[tool.uv.sources]
mollymawk = { workspace = true }

[tool.uv.workspace]
members = [
  "packages/mollymawk"
]

Optional dependencies#

It is common for projects that are published as libraries to make some features optional to reduce the default dependency tree. For example, Pandas has an excel extra and a plot extra to avoid installation of Excel parsers and matplotlib unless someone explicitly requires them. Extras are requested with the package[<extra>] syntax, e.g., pandas[plot, excel].

Optional dependencies are specified in [project.optional-dependencies], a TOML table that maps from extra name to its dependencies, following PEP 508 syntax.

Optional dependencies can have entries in tool.uv.sources the same as normal dependencies.

pyproject.toml
[project]
name = "pandas"
version = "1.0.0"

[project.optional-dependencies]
plot = [
  "matplotlib>=3.6.3"
]
excel = [
  "odfpy>=1.4.1",
  "openpyxl>=3.1.0",
  "python-calamine>=0.1.7",
  "pyxlsb>=1.0.10",
  "xlrd>=2.0.1",
  "xlsxwriter>=3.0.5"
]

To add an optional dependency, use the --optional <extra> option:

$ uv add httpx --optional network

Development dependencies#

Unlike optional dependencies, development dependencies are local-only and will not be included in the project requirements when published to PyPI or other indexes. As such, development dependencies are included under [tool.uv] instead of [project].

Development dependencies can have entries in tool.uv.sources the same as normal dependencies.

pyproject.toml
[tool.uv]
dev-dependencies = [
  "pytest >=8.1.1,<9"
]

To add a development dependency, include the --dev flag:

$ uv add ruff --dev

PEP 508#

PEP 508 defines a syntax for dependency specification. It is composed of, in order:

  • The dependency name
  • The extras you want (optional)
  • The version specifier
  • An environment marker (optional)

The version specifiers are comma separated and added together, e.g., foo >=1.2.3,<2,!=1.4.0 is interpreted as "a version of foo that's at least 1.2.3, but less than 2, and not 1.4.0".

Specifiers are padded with trailing zeros if required, so foo ==2 matches foo 2.0.0, too.

A star can be used for the last digit with equals, e.g. foo ==2.1.* will accept any release from the 2.1 series. Similarly, ~= matches where the last digit is equal or higher, e.g., foo ~=1.2 is equal to foo >=1.2,<2, and foo ~=1.2.3 is equal to foo >=1.2.3,<1.3.

Extras are comma-separated in square bracket between name and version, e.g., pandas[excel,plot] ==2.2. Whitespace between extra names is ignored.

Some dependencies are only required in specific environments, e.g., a specific Python version or operating system. For example to install the importlib-metadata backport for the importlib.metadata module, use importlib-metadata >=7.1.0,<8; python_version < '3.10'. To install colorama on Windows (but omit it on other platforms), use colorama >=0.4.6,<5; platform_system == "Windows".

Markers are combined with and, or, and parentheses, e.g., aiohttp >=3.7.4,<4; (sys_platform != 'win32' or implementation_name != 'pypy') and python_version >= '3.10'. Note that versions within markers must be quoted, while versions outside of markers must not be quoted.

Editable dependencies#

A regular installation of a directory with a Python package first builds a wheel and then installs that wheel into your virtual environment, copying all source files. When the package source files are edited, the virtual environment will contain outdated versions.

Editable installations solve this problem by adding a link to the project within the virtual environment (a .pth file), which instructs the interpreter to include the source files directly.

There are some limitations to editables (mainly: the build backend needs to support them, and native modules aren't recompiled before import), but they are useful for development, as the virtual environment will always use the latest changes to the package.

uv uses editable installation for workspace packages by default.

To add an editable dependency, use the --editable flag:

$ uv add --editable ./path/foo

Or, to opt-out of using an editable dependency in a workspace:

$ uv add --no-editable ./path/foo