Python SDK

RBS provides first-class Python support with hermetic toolchains, automatic dependency resolution, test coverage enforcement, and linting — all without requiring pip, venv, or any system-installed Python.

Setup

Toolchain

load("@rbs//python/toolchain.rbs", "python_toolchain")

python_toolchain(name = "python3", version = "3.12")

Dependencies

Define external packages using py_repository. RBS resolves and caches them hermetically.

load("@rbs//python/dependencies.rbs", "py_repository")

py_repository(name = "django_repo", package = "django", version = "5.0.1")
py_repository(name = "requests_repo", package = "requests", version = "2.32.4")
py_repository(name = "gunicorn_repo", package = "gunicorn", version = "23.0.0")

Linting

load("@rbs//python/lint.rbs", "register_python_linters")
register_python_linters()

Rules

`py_library`

Creates a reusable Python library that other targets can depend on.

load("@rbs//python/rules.rbs", "py_library")

py_library(
    name = "calculator",
    srcs = ["src/calculator.py"],
)

py_library(
    name = "string_utils",
    srcs = ["src/string_utils.py"],
)

Attribute	Type	Description
`name`	string	Unique target name (required).
`srcs`	list	Python source files.
`deps`	list	Dependencies (local targets or `@external://` references).

`py_binary`

Creates an executable Python application with all dependencies bundled.

load("@rbs//python/rules.rbs", "py_binary")

py_binary(
    name = "app",
    srcs = ["src/main.py"],
    main = "src/main.py",
    deps = [":calculator", ":string_utils"],
)

Attribute	Type	Description
`name`	string	Unique target name (required).
`srcs`	list	Python source files.
`main`	string	Entry point file (required).
`deps`	list	Dependencies.
`args`	list	Default arguments passed to the binary.
`env`	dict	Environment variables.

`py_test`

Runs Python tests with optional coverage thresholds. Pytest is auto-included — no manual dependency needed.

load("@rbs//python/rules.rbs", "py_test")

# Basic test
py_test(
    name = "calculator_test",
    srcs = ["tests/test_calculator.py"],
    deps = [":calculator"],
)

# Test with coverage enforcement — FAILS if below threshold
py_test(
    name = "calculator_coverage_test",
    srcs = ["tests/test_calculator.py"],
    deps = [":calculator"],
    min_line_coverage = 85,
    min_branch_coverage = 75,
    min_function_coverage = 80,
    size = "small",
    timeout = 60,
)

Attribute	Type	Description
`name`	string	Unique target name (required).
`srcs`	list	Test source files.
`deps`	list	Dependencies (libraries under test).
`test_runner`	string	`"pytest"` (default) or `"unittest"`.
`min_line_coverage`	int	Minimum line coverage percentage. Test fails if below.
`min_branch_coverage`	int	Minimum branch coverage percentage.
`min_function_coverage`	int	Minimum function coverage percentage.
`size`	string	Test size (`"small"`, `"medium"`, `"large"`).
`timeout`	int	Timeout in seconds.

`py_lint`

Runs linters (Black + isort by default) on Python source files.

load("@rbs//python/lint.rbs", "py_lint")

py_lint(
    name = "lint",
    srcs = glob(["**/*.py"], exclude = [".rbs/**", "__pycache__/**"]),
)

# Auto-fix mode
py_lint(
    name = "lint_fix",
    srcs = glob(["**/*.py"], exclude = [".rbs/**", "__pycache__/**"]),
    fix = True,
)

Attribute	Type	Description
`name`	string	Unique target name (required).
`srcs`	list	Source files to lint.
`fix`	bool	Auto-fix lint issues (default `False`).

Example: Django Blog

A complete Django application with development/production servers, management commands, and linting.

WORKSPACE.rbs
BUILD.rbs
Commands

load("@rbs//python/toolchain.rbs", "python_toolchain")
load("@rbs//python/lint.rbs", "register_python_linters")
load("@rbs//python/dependencies.rbs", "py_repository")

python_toolchain(name = "python3", version = "3.12")
register_python_linters()

py_repository(name = "django_repo", package = "django", version = "5.0.1")
py_repository(name = "gunicorn_repo", package = "gunicorn", version = "23.0.0")
py_repository(name = "whitenoise_repo", package = "whitenoise", version = "6.6.0")
py_repository(name = "pillow_repo", package = "pillow", version = "10.2.0")
py_repository(name = "requests_repo", package = "requests", version = "2.32.4")

load("@rbs//python/rules.rbs", "py_binary", "py_library")
load("@rbs//python/lint.rbs", "py_lint")

py_library(
    name = "blog_app",
    srcs = glob(["blog/*.py"]),
    deps = [":django_repo", ":pillow_repo"],
)

py_library(
    name = "django_config",
    srcs = glob(["django_blog/*.py"]),
    deps = [":django_repo", ":whitenoise_repo", ":requests_repo"],
)

# Development server
py_binary(
    name = "dev_server",
    srcs = ["manage.py"],
    main = "manage.py",
    args = ["runserver", "8001"],
    deps = [":blog_app", ":django_config", ":django_repo"],
    env = {"DJANGO_SETTINGS_MODULE": "django_blog.settings", "DEBUG": "True"},
)

# Production server (Gunicorn)
py_binary(
    name = "prod_server",
    srcs = ["gunicorn_config.py"],
    main = "gunicorn_config.py",
    deps = [":blog_app", ":django_config", ":django_repo", ":gunicorn_repo", ":whitenoise_repo"],
    env = {"DJANGO_SETTINGS_MODULE": "django_blog.settings", "DEBUG": "False"},
)

# Database migrations
py_binary(
    name = "migrate",
    srcs = ["manage.py"],
    main = "manage.py",
    args = ["migrate"],
    deps = [":blog_app", ":django_config", ":django_repo"],
    env = {"DJANGO_SETTINGS_MODULE": "django_blog.settings"},
)

# Lint
py_lint(
    name = "lint",
    srcs = glob(["**/*.py"], exclude = [".rbs/**", "venv/**", "__pycache__/**"]),
)

rbs run dev_server              # Start development server
rbs run prod_server             # Start production server
rbs run migrate                 # Run database migrations
rbs build lint                  # Check code style

Commands

rbs build app                          # Build binary
rbs run dev_server                     # Run development server
rbs test calculator_test               # Run tests
rbs test calculator_coverage_test      # Run tests with coverage enforcement
rbs coverage calculator_test           # Generate coverage report
rbs build lint                         # Run linter

Language SDKs

Platform SDKs

Python SDK

Python SDK

Setup

Toolchain

Dependencies

Linting

Rules

`py_library`

`py_binary`

`py_test`

`py_lint`

Example: Django Blog

Commands

​Python SDK

​Setup

​Toolchain

​Dependencies

​Linting

​Rules

​py_library

​py_binary

​py_test

​py_lint

​Example: Django Blog

​Commands

Python SDK

Setup

Toolchain

Dependencies

Linting

Rules

`py_library`

`py_binary`

`py_test`

`py_lint`

Example: Django Blog

Commands