> ## Documentation Index > Fetch the complete documentation index at: https://docs.reasonos.com/llms.txt > Use this file to discover all available pages before exploring further. # Python SDK > Build, test, and deploy Python applications with RBS — hermetic toolchains, automatic dependency management, and built-in coverage. # 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 Register a Python toolchain in your `WORKSPACE.rbs`. RBS automatically downloads and manages the interpreter. ```python filename="WORKSPACE.rbs" theme={null} 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. ```python filename="WORKSPACE.rbs" theme={null} 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 Register Python linters (Black, isort, Flake8, Ruff) for workspace-wide use: ```python filename="WORKSPACE.rbs" theme={null} 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. ```python theme={null} 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. ```python theme={null} 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. ```python theme={null} 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. ```python theme={null} 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. ```python theme={null} 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") ``` ```python theme={null} 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__/**"]), ) ``` ```bash theme={null} 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 ```bash theme={null} 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 ```