Poet: Dependency Management for Python

Poet helps you declare, manage and install dependencies of Python projects, ensuring you have the right stack everywhere.

The package is highly experimental at the moment so expect things to change and break. However, if you feel adventurous I'd gladly appreciate feedback and pull requests.

Installation

pip install pypoet

Enable tab completion for Bash, Fish, or Zsh

poet supports generating completion scripts for Bash, Fish, and Zsh. See poet help completions for full details, but the gist is as simple as using one of the following:

# Bash
$ poet completions bash > /etc/bash_completion.d/poet.bash-completion

# Bash (macOS/Homebrew)
$ poet completions bash > $(brew --prefix)/etc/bash_completion.d/poet.bash-completion

# Fish
$ poet completions fish > ~/.config/fish/completions/poet.fish

# Zsh
$ poet completions zsh > ~/.zfunc/_poet

Note: you may need to restart your shell in order for the changes to take effect.

For zsh, you must then add the following line in your ~/.zshrc before compinit:

fpath+=~/.zfunc

Introduction

poet is a tool to handle dependencies installation, building and packaging of Python packages. It only needs one file to do all of that: poetry.toml.

[package]
name = "pypoet"
version = "0.1.0"
description = "Poet helps you declare, manage and install dependencies of Python projects, ensuring you have the right stack everywhere."

license = "MIT"

authors = [
    "Sébastien Eustace "
]

readme = 'README.md'

repository = "https://github.com/sdispater/poet"
homepage = "https://github.com/sdispater/poet"

keywords = ['packaging', 'poet']

include = ['poet/**/*', 'LICENSE']

python = ["~2.7", "^3.2"]


[dependencies]
toml = "^0.9"
requests = "^2.13"
semantic_version = "^2.6"
pygments = "^2.2"
twine = "^1.8"
wheel = "^0.29"
pip-tools = "^1.8.2"
cleo = { git = "https://github.com/sdispater/cleo.git", branch = "master" }

[dev-dependencies]
pytest = "^3.0"
pytest-cov = "^2.4"
coverage = "<4.0"
httpretty = "^0.8.14"

[scripts]
poet = 'poet:app.run'

There are some things we can notice here:

• It will try to enforce semantic versioning as the best practice in version naming.
• You can specify the readme, included and excluded files: no more MANIFEST.in. poet will also use VCS ignore files (like .gitignore) to populate the exclude section.
• Keywords (up to 5) can be specified and will act as tags on the packaging site.
• The dependencies sections support caret, tilde, wildcard, inequality and multiple requirements.
• You must specify the python versions for which your package is compatible.

poet will also detect if you are inside a virtualenv and install the packages accordingly. So, poet can be installed globally and used everywhere.

Why?

Packaging system and dependency management in Python is rather convoluted and hard to understand for newcomers. Even for seasoned developers it might be cumbersome at times to create all files needed in a Python project: setup.py, requirements.txt, setup.cfg, MANIFEST.in.

So I wanted a tool that would limit everything to a single configuration file to do everything: dependency management, packaging and publishing.

It takes inspiration in tools that exist in other languages, like composer (PHP) or cargo (Rust).

Note that there is no magic here, poet uses existing tools (pip, twine, setuptools, distutils, pip-tools) under the hood to achieve that in a more intuitive way.

Commands

init

This command will help you create a poetry.toml file interactively by prompting you to provide basic information about your package.

It will interactively ask you to fill in the fields, while using some smart defaults.

poet init

However, if you just want a basic template and fill the information directly, you can just do:

poet init default

Options

• --name: Name of the package.
• --description: Description of the package.
• --author: Author of the package.
• --require: Package to require with a version constraint. Should be in format foo:1.0.0.
• --require-dev: Development requirements, see --require.
• --index: Index to use when searching for packages.

install

The install command reads the poetry.toml file from the current directory, resolves the dependencies, and installs them.

poet install

If there is a poetry.lock file in the current directory, it will use the exact versions from there instead of resolving them. This ensures that everyone using the library will get the same versions of the dependencies.

If there is no poetry.lock file, Poet will create one after dependency resolution.

You can specify to the command that yo do not want the development dependencies installed by passing the --no-dev option.

poet install --no-dev

You can also specify the features you want installed by passing the --f|--features option (See Features for more info)

poet install --features "mysql pgsql"
poet install -f mysql -f pgsql

Options

• --no-dev: Do not install dev dependencies.
• -f|--features: Features to install (multiple values allowed).
• --no-progress: Removes the progress display that can mess with some terminals or scripts which don't handle backspace characters.
• --index: The index to use when installing packages.

update

In order to get the latest versions of the dependencies and to update the poetry.lock file, you should use the update command.

poet update

This will resolve all dependencies of the project and write the exact versions into poetry.lock.

If you just want to update a few packages and not all, you can list them as such:

poet update requests toml

Options

• --no-progress: Removes the progress display that can mess with some terminals or scripts which don't handle backspace characters.
• --index: The index to use when installing packages.

package

The package command builds the source and wheels archives.

Options

• --no-universal: Do not build a universal wheel.
• --no-wheels: Build only the source package.
• -c|--clean: Make a clean package.

publish

This command builds (if not already built) and publishes the package to the remote repository.

It will automatically register the package before uploading if this is the first time it is submitted.

Options

• -r|--repository: The repository to register the package to (default: pypi). Should match a section of your ~/.pypirc file.

search

This command searches for packages on a remote index.

poet search requests pendulum

Options

• -i|--index: The index to use.
• -N|--only-name: Search only in name.

lock

This command locks (without installing) the dependencies specified in poetry.toml.

poet lock

Options

• --no-progress: Removes the progress display that can mess with some terminals or scripts which don't handle backspace characters.
• -i|--index: The index to use.
• -f|--force: Force locking.

check

The check command will check if the poetry.toml file is valid.

poet check

The poetry.toml file

A poetry.toml file is composed of multiple sections.

package

This section describes the specifics of the package

name

The name of the package. Required

version

The version of the package. Required

This should follow semantic versioning. However it will not be enforced and you remain free to follow another specification.

description

A short description of the package. Required

license

The license of the package.

The recommended notation for the most common licenses is (alphabetical):

• Apache-2.0
• BSD-2-Clause
• BSD-3-Clause
• BSD-4-Clause
• GPL-2.0
• GPL-2.0+
• GPL-3.0
• GPL-3.0+
• LGPL-2.1
• LGPL-2.1+
• LGPL-3.0
• LGPL-3.0+
• MIT

Optional, but it is highly recommended to supply this. More identifiers are listed at the SPDX Open Source License Registry.

authors

The authors of the package. This is a list of authors and should contain at least one author.

Authors must be in the form name .

readme

The readme file of the package. Required

The file can be either README.rst or README.md. If it's a markdown file you have to install the pandoc utility so that it can be automatically converted to a RestructuredText file.

You also need to have the pypandoc package installed. If you install poet via pip you can use the markdown-readme extra to do so.

pip install pypoet[markdown-readme]

homepage

An URL to the website of the project. Optional

repository

An URL to the repository of the project. Optional

documentation

An URL to the documentation of the project. Optional

keywords

A list of keywords (max: 5) that the package is related to. Optional

python

A list of Python versions for which the package is compatible. Required

include and exclude

A list of patterns that will be included in the final package.

You can explicitly specify to Poet that a set of globs should be ignored or included for the purposes of packaging. The globs specified in the exclude field identify a set of files that are not included when a package is built.

If a VCS is being used for a package, the exclude field will be seeded with the VCS’ ignore settings (.gitignore for git for example).

[package]
# ...
include = ["package/**/*.py", "package/**/.c"]

exclude = ["package/excluded.py"]

If you packages lies elsewhere (say in a src directory), you can tell poet to find them from there:

include = { from = 'src', include = '**/*' }

Similarly, you can tell that the src directory represent the foo package:

include = { from = 'src', include = '**/*', as = 'foo' }

dependencies and dev-dependencies

Poet is configured to look for dependencies on PyPi by default. Only the name and a version string are required in this case.

[dependencies]
requests = "^2.13.0"

Caret requirement

Caret requirements allow SemVer compatible updates to a specified version. An update is allowed if the new version number does not modify the left-most non-zero digit in the major, minor, patch grouping. In this case, if we ran poet update requests, poet would update us to version 2.14.0 if it was available, but would not update us to 3.0.0. If instead we had specified the version string as ^0.1.13, poet would update to 0.1.14 but not 0.2.0. 0.0.x is not considered compatible with any other version.

Here are some more examples of caret requirements and the versions that would be allowed with them:

^1.2.3 := >=1.2.3 <2.0.0
^1.2 := >=1.2.0 <2.0.0
^1 := >=1.0.0 <2.0.0
^0.2.3 := >=0.2.3 <0.3.0
^0.0.3 := >=0.0.3 <0.0.4
^0.0 := >=0.0.0 <0.1.0
^0 := >=0.0.0 <1.0.0

Tilde requirements

Tilde requirements specify a minimal version with some ability to update. If you specify a major, minor, and patch version or only a major and minor version, only patch-level changes are allowed. If you only specify a major version, then minor- and patch-level changes are allowed.

~1.2.3 is an example of a tilde requirement.

~1.2.3 := >=1.2.3 <1.3.0
~1.2 := >=1.2.0 <1.3.0
~1 := >=1.0.0 <2.0.0

Wildcard requirements

Wildcard requirements allow for any version where the wildcard is positioned.

*, 1.* and 1.2.* are examples of wildcard requirements.

* := >=0.0.0
1.* := >=1.0.0 <2.0.0
1.2.* := >=1.2.0 <1.3.0

Inequality requirements

Inequality requirements allow manually specifying a version range or an exact version to depend on.

Here are some examples of inequality requirements:

>= 1.2.0
> 1
< 2
!= 1.2.3

Multiple requirements

Multiple version requirements can also be separated with a comma, e.g. >= 1.2, < 1.5.

git dependencies

To depend on a library located in a git repository, the minimum information you need to specify is the location of the repository with the git key:

[dependencies]
requests = { git = "https://github.com/kennethreitz/requests.git" }

Since we haven’t specified any other information, Poet assumes that we intend to use the latest commit on the master branch to build our project. You can combine the git key with the rev, tag, or branch keys to specify something else. Here's an example of specifying that you want to use the latest commit on a branch named next:

[dependencies]
requests = { git = "https://github.com/kennethreitz/requests.git", branch = "next" }

Python restricted dependencies

You can also specify that a dependency should be installed only for specific Python versions:

[dependencies]
pathlib2 = { version = "^2.2", python = "~2.7" }

[dependencies]
pathlib2 = { version = "^2.2", python = ["~2.7", "^3.2"] }

scripts

This section describe the scripts or executable that will be installed when installing the package

[scripts]
poet = 'poet:app.run'

Here, we will have the poet script installed which will execute app.run in the poet package.

features

Poet supports features to allow expression of:

• optional dependencies, which enhance a package, but are not required; and
• clusters of optional dependencies.

[package]
name = "awesome"

[features]
mysql = ["mysqlclient"]
pgsql = ["psycopg2"]

[dependencies]
# These packages are mandatory and form the core of this package’s distribution.
mandatory = "^1.0"

# A list of all of the optional dependencies, some of which are included in the
# above `features`. They can be opted into by apps.
psycopg2 = { version = "^2.7", optional = true }
mysqlclient = { version = "^1.3", optional = true }

When installing packages, you can specify features by using the -f|--features option:

poet install --features "mysql pgsql"
poet install -f mysql -f pgsql

Resources

• Official Website
• Issue Tracker