Bazel Python Rules

Rules

• pip_import
• py_library
• py_binary
• py_test

Overview

This repository provides Python rules for Bazel. Currently, support for rules that are available from Bazel core are simple aliases to that bundled functionality. On top of that, this repository provides support for installing dependencies typically managed via pip.

Setup

Add the following to your WORKSPACE file to add the external repositories:

git_repository(
    name = "io_bazel_rules_python",
    remote = "https://github.com/bazelbuild/rules_python.git",
    commit = "{HEAD}",
)

# Only needed for PIP support:
load("//python:pip.bzl", "pip_repositories")

pip_repositories()

Then in your BUILD files load the python rules with:

load(
  "@io_bazel_rules_python//python:python.bzl",
  "py_binary", "py_library", "py_test",
)

py_binary(
  name = "main",
  ...
)

Importing pip dependencies

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("@io_bazel_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()

Consuming pip dependencies

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 packages method, which can be used directly in deps=[] to reference an imported py_library.

load("@my_deps//:requirements.txt", "packages")

py_library(
    name = "mylib",
    srcs = ["mylib.py"],
    deps = [
        ":myotherlib",
	# This takes the name as specified in requirements.txt
	packages("importeddep"),
    ]
)