Managing dependencies

Managing dependencies #

Dependency groups #

Poetry provides a way to organize your dependencies by groups. For instance, you might have dependencies that are only needed to test your project or to build the documentation.

To declare a new dependency group, use a<group> section where <group> is the name of your dependency group (for instance, test):

[]  # This part can be left out

pytest = "^6.0.0"
pytest-mock = "*"

All dependencies must be compatible with each other across groups since they will be resolved regardless of whether they are required for installation or not (see Installing group dependencies).

Think of dependency groups as labels associated with your dependencies: they don’t have any bearings on whether their dependencies will be resolved and installed by default, they are simply a way to organize the dependencies logically.


The dependencies declared in tool.poetry.dependencies are part of an implicit main group.

[tool.poetry.dependencies]  # main dependency group
httpx = "*"
pendulum = "*"

[] pytest = "^6.0.0" pytest-mock = "*"


Dependency groups, other than the implicit main group, must only contain dependencies you need in your development process. Installing them is only possible by using Poetry.

To declare a set of dependencies, which add additional functionality to the project during runtime, use extras instead. Extras can be installed by the end user using pip.


A note about defining a dev dependencies group

The proper way to define a dev dependencies group since Poetry 1.2.0 is the following:

pytest = "^6.0.0"
pytest-mock = "*"

This group notation is preferred since Poetry 1.2.0 and not usable in earlier versions. For backwards compatibility with older versions of Poetry, any dependency declared in the dev-dependencies section will automatically be added to the dev group. So the above and following notations are equivalent:

# Poetry pre-1.2.x style, understood by Poetry 1.0–1.2
pytest = "^6.0.0"
pytest-mock = "*"

Poetry will slowly transition away from the dev-dependencies notation which will soon be deprecated, so it’s advised to migrate your existing development dependencies to the new group notation.

Optional groups #

A dependency group can be declared as optional. This makes sense when you have a group of dependencies that are only required in a particular environment or for a specific purpose.

optional = true

mkdocs = "*"

Optional groups can be installed in addition to the default dependencies by using the --with option of the install command.

poetry install --with docs
Optional group dependencies will still be resolved alongside other dependencies, so special care should be taken to ensure they are compatible with each other.

Adding a dependency to a group #

The add command is the preferred way to add dependencies to a group. This is done by using the --group (-G) option.

poetry add pytest --group test

If the group does not already exist, it will be created automatically.

Installing group dependencies #

By default, dependencies across all non-optional groups will be installed when executing poetry install.

The default set of dependencies for a project includes the implicit main group defined in tool.poetry.dependencies as well as all groups that are not explicitly marked as an optional group.

You can exclude one or more groups with the --without option:

poetry install --without test,docs

You can also opt in optional groups by using the --with option:

poetry install --with docs

When used together, --without takes precedence over --with. For example, the following command will only install the dependencies specified in the optional test group.

poetry install --with test,docs --without docs

Finally, in some case you might want to install only specific groups of dependencies without installing the default set of dependencies. For that purpose, you can use the --only option.

poetry install --only docs

If you only want to install the project’s runtime dependencies, you can do so with the --only main notation:

poetry install --only main

If you want to install the project root, and no other dependencies, you can use the --only-root option.

poetry install --only-root

Removing dependencies from a group #

The remove command supports a --group option to remove packages from a specific group:

poetry remove mkdocs --group docs

Synchronizing dependencies #

Poetry supports what’s called dependency synchronization. Dependency synchronization ensures that the locked dependencies in the poetry.lock file are the only ones present in the environment, removing anything that’s not necessary.

This is done by using the --sync option of the install command:

poetry install --sync

The --sync option can be combined with any dependency groups related options to synchronize the environment with specific groups. Note that extras are separate. Any extras not selected for install are always removed, regardless of --sync.

poetry install --without dev --sync
poetry install --with docs --sync
poetry install --only dev
The --sync option replaces the --remove-untracked option which is now deprecated.

Layering optional groups #

When you omit the --sync option, you can install any subset of optional groups without removing those that are already installed. This is very useful, for example, in multi-stage Docker builds, where you run poetry install multiple times in different build stages.