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python-poetry
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Description

Python dependency management and packaging made easy.

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Poetry: Dependency Management for Python

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

Poetry Install

It supports Python 2.7 and 3.5+.

Note: Python 2.7 and 3.5 will no longer be supported in the next feature release (1.2). You should consider updating your Python version to a supported one.

Tests Status

The complete documentation is available on the official website.

Installation

Poetry provides a custom installer that will install

poetry
isolated from the rest of your system by vendorizing its dependencies. This is the recommended way of installing
poetry
.
curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py | python

Alternatively, you can download the

get-poetry.py
file and execute it separately.

The setup script must be able to find one of following executables in your shell's path environment:

  • python
    (which can be a py3 or py2 interpreter)
  • python3
  • py.exe -3
    (Windows)
  • py.exe -2
    (Windows)

If you want to install prerelease versions, you can do so by passing

--preview
to
get-poetry.py
:
python get-poetry.py --preview

Similarly, if you want to install a specific version, you can use

--version
:
python get-poetry.py --version 0.7.0

Using

pip
to install
poetry
is also possible.
pip install --user poetry

Be aware, however, that it will also install poetry's dependencies which might cause conflicts.

Updating
poetry

Updating poetry to the latest stable version is as simple as calling the

self update
command.
poetry self update

If you want to install prerelease versions, you can use the

--preview
option.
poetry self update --preview

And finally, if you want to install a specific version you can pass it as an argument to

self update
.
poetry self update 1.0.0

Note:

If you are still on poetry version < 1.0 use `poetry self:update` instead.

Enable tab completion for Bash, Fish, or Zsh

poetry
supports generating completion scripts for Bash, Fish, and Zsh. See
poetry help completions
for full details, but the gist is as simple as using one of the following:
# Bash
poetry completions bash > /etc/bash_completion.d/poetry.bash-completion

Bash (Homebrew)

poetry completions bash > $(brew --prefix)/etc/bash_completion.d/poetry.bash-completion

Fish

poetry completions fish > ~/.config/fish/completions/poetry.fish

Fish (Homebrew)

poetry completions fish > (brew --prefix)/share/fish/vendor_completions.d/poetry.fish

Zsh

poetry completions zsh > ~/.zfunc/_poetry

Zsh (Homebrew)

poetry completions zsh > $(brew --prefix)/share/zsh/site-functions/_poetry

Zsh (Oh-My-Zsh)

mkdir $ZSH_CUSTOM/plugins/poetry poetry completions zsh > $ZSH_CUSTOM/plugins/poetry/_poetry

Zsh (prezto)

poetry completions zsh > ~/.zprezto/modules/completion/external/src/_poetry

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
(not for homebrew setup):
fpath+=~/.zfunc

Introduction

poetry
is a tool to handle dependency installation as well as building and packaging of Python packages. It only needs one file to do all of that: the new, standardized
pyproject.toml
.

In other words, poetry uses

pyproject.toml
to replace
setup.py
,
requirements.txt
,
setup.cfg
,
MANIFEST.in
and the newly added
Pipfile
.
[tool.poetry]
name = "my-package"
version = "0.1.0"
description = "The description of the package"

license = "MIT"

authors = [ "Sébastien Eustace " ]

readme = 'README.md' # Markdown files are supported

repository = "https://github.com/python-poetry/poetry" homepage = "https://github.com/python-poetry/poetry"

keywords = ['packaging', 'poetry']

[tool.poetry.dependencies] python = "~2.7 || ^3.2" # Compatible python versions must be declared here toml = "^0.9"

Dependencies with extras

requests = { version = "^2.13", extras = [ "security" ] }

Python specific dependencies with prereleases allowed

pathlib2 = { version = "^2.2", python = "~2.7", allow-prereleases = true }

Git dependencies

cleo = { git = "https://github.com/sdispater/cleo.git", branch = "master" }

Optional dependencies (extras)

pendulum = { version = "^1.4", optional = true }

[tool.poetry.dev-dependencies] pytest = "^3.0" pytest-cov = "^2.4"

[tool.poetry.scripts] my-script = 'my_package:main'

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
    .
    poetry
    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.

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

poetry
also comes with a full fledged dependency resolution library.

Why?

Packaging systems and dependency management in Python are 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
and the newly added
Pipfile
.

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

It takes inspiration in tools that exist in other languages, like

composer
(PHP) or
cargo
(Rust).

And, finally, I started

poetry
to bring another exhaustive dependency resolver to the Python community apart from Conda's.

What about Pipenv?

In short: I do not like the CLI it provides, or some of the decisions made, and I think we can make a better and more intuitive one. Here are a few things that I don't like.

Dependency resolution

The dependency resolution is erratic and will fail even if there is a solution. Let's take an example:

pipenv install oslo.utils==1.4.0

will fail with this error:

Could not find a version that matches pbr!=0.7,!=2.1.0,<1.0,>=0.6,>=2.0.0

while Poetry will get you the right set of packages:

poetry add oslo.utils=1.4.0

results in :

  - Installing pytz (2018.3)
  - Installing netifaces (0.10.6)
  - Installing netaddr (0.7.19)
  - Installing oslo.i18n (2.1.0)
  - Installing iso8601 (0.1.12)
  - Installing six (1.11.0)
  - Installing babel (2.5.3)
  - Installing pbr (0.11.1)
  - Installing oslo.utils (1.4.0)

This is possible thanks to the efficient dependency resolver at the heart of Poetry.

Here is a breakdown of what exactly happens here:

oslo.utils (1.4.0)
depends on:
  • pbr (>=0.6,!=0.7,<1.0)
  • Babel (>=1.3)
  • six (>=1.9.0)
  • iso8601 (>=0.1.9)
  • oslo.i18n (>=1.3.0)
  • netaddr (>=0.7.12)
  • netifaces (>=0.10.4)

What interests us is

pbr (>=0.6,!=0.7,<1.0)
.

At this point, poetry will choose

pbr==0.11.1
which is the latest version that matches the constraint.

Next it will try to select

oslo.i18n==3.20.0
which is the latest version that matches
oslo.i18n (>=1.3.0)
.

However this version requires

pbr (!=2.1.0,>=2.0.0)
which is incompatible with
pbr==0.11.1
, so
poetry
will try to find a version of
oslo.i18n
that satisfies
pbr (>=0.6,!=0.7,<1.0)
.

By analyzing the releases of

oslo.i18n
, it will find
oslo.i18n==2.1.0
which requires
pbr (>=0.11,<2.0)
. At this point the rest of the resolution is straightforward since there is no more conflict.

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