Status: This is ALPHA software.
- 2019-07-26: The canonical name of this repo has been changed from
@io_bazel_rules_pythonto just@rules_python, in accordance with convention. Please update your WORKSPACE file and labels that reference this repo accordingly.
This repository provides two sets of Python rules for Bazel. The core rules
provide the essential library, binary, test, and toolchain rules that are
expected for any language supported in Bazel. The packaging rules provide
support for integration with dependencies that, in a non-Bazel environment,
would typically be managed by pip.
Historically, the core rules have been bundled with Bazel itself. The Bazel
team is in the process of transitioning these rules to live in
bazelbuild/rules_python instead. In the meantime, all users of Python rules in
Bazel should migrate their builds to load these rules and their related symbols
(PyInfo, etc.) from @rules_python instead of using built-ins or
@bazel_tools//tools/python.
To use this repository, first modify your WORKSPACE file to load it and call
the initialization functions as needed:
load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")
git_repository(
name = "rules_python",
remote = "https://github.com/bazelbuild/rules_python.git",
# NOT VALID! Replace this with a Git commit SHA.
commit = "{HEAD}",
)
# This call should always be present.
load("@rules_python//python:repositories.bzl", "py_repositories")
py_repositories()
# This one is only needed if you're using the packaging rules.
load("@rules_python//python:pip.bzl", "pip_repositories")
pip_repositories()Then in your BUILD files, load the core rules as needed with:
load("@rules_python//python:defs.bzl", "py_binary")
py_binary(
name = "main",
...
)These rules are designed to have developers continue using requirements.txt
to express their dependencies in a Python idiomatic manner. These dependencies
are imported into the Bazel dependency graph via a two-phased process in
WORKSPACE:
load("@rules_python//python:pip.bzl", "pip_import")
# This rule translates the specified requirements.txt into
# @my_deps//:requirements.bzl, which itself exposes a pip_install method.
pip_import(
name = "my_deps",
requirements = "//path/to:requirements.txt",
)
# Load the pip_install symbol for my_deps, and create the dependencies'
# repositories.
load("@my_deps//:requirements.bzl", "pip_install")
pip_install()Once a set of dependencies has been imported via pip_import and pip_install
we can start consuming them in our py_{binary,library,test} rules. In support
of this, the generated requirements.bzl also contains a requirement method,
which can be used directly in deps=[] to reference an imported py_library.
load("@my_deps//:requirements.bzl", "requirement")
py_library(
name = "mylib",
srcs = ["mylib.py"],
deps = [
":myotherlib",
# This takes the name as specified in requirements.txt
requirement("importeddep"),
]
)It is notable that whl_library rules imported via pip_import are canonically
named, following the pattern: pypi__{distribution}_{version}. Characters in
these components that are illegal in Bazel label names (e.g. -, .) are
replaced with _.
This canonical naming helps avoid redundant work to import the same library
multiple times. It is expected that this naming will remain stable, so folks
should be able to reliably depend directly on e.g. @pypi__futures_3_1_1//:pkg
for dependencies, however, it is recommended that folks stick with the
requirement pattern in case the need arises for us to make changes to this
format in the future.
"Extras"
will have a target of the extra name (in place of pkg above).
All of the content under docs/ besides the BUILD file is generated with
Stardoc. To regenerate the documentation, simply run
./update_docs.shfrom the repository root.
The piptool.par and whltool.par files underneath tools/ are compiled
versions of the Python scripts under the rules_python/ directory. We need to
check in built artifacts because they are executed during WORKSPACE
evaluation, before Bazel itself is able to build anything from source.
The .par files need to be regenerated whenever their sources are updated. This can be done by running
./update_tools.shfrom the repository root. However, since these files contain compiled code, we do not accept commits that modify them from untrusted sources. If you submit a pull request that modifies the sources and we accept the changes, we will regenerate these files for you before merging.