mxaccessgw/docs/style-guides/PythonStyleGuide.md

Python Style Guide

This guide defines Python conventions for the MXAccess Gateway Python package, CLI, and tests.

Baseline

• Target modern supported Python versions defined by pyproject.toml.
• Use pyproject.toml for package metadata and tool configuration.
• Use type hints for public APIs and non-trivial internal functions.
• Run the configured formatter and linter when the package is available.
• Keep generated protobuf code separate from handwritten modules.

Source Documentation

• Maintain the existing documentation style in the file, package, and surrounding component.
• Write comments that include business-specific or domain-specific context when that context is available from the code, surrounding docs, or naming.
• Use docstrings for public classes, functions, and modules when behavior, parity constraints, or security requirements are not obvious from the name and type hints.
• Avoid comments that restate syntax or control flow.

Package Structure

• Put library code under src/zb_mom_ww_mxgateway/.
• Put CLI entry points under src/zb_mom_ww_mxgateway_cli/.
• Keep generated protobuf modules under a clearly named generated package.
• Avoid import side effects that open channels, read environment variables, or start background tasks.

Naming

• Use snake_case for functions, variables, modules, and methods.
• Use PascalCase for classes and exceptions.
• Use UPPER_SNAKE_CASE for constants.
• Keep MXAccess names recognizable in public APIs, even when Python wrappers use idiomatic method names.

Async

• Make the client async-first.
• Use async context managers for clients and sessions when practical.
• Cancel gRPC streams when async iteration is canceled.
• Document that canceling a Python task does not abort an in-flight MXAccess COM call inside the worker.

Errors

• Use typed exceptions for transport, authentication, authorization, session, worker, command, and MXAccess failures.
• Attach raw protobuf replies to command exceptions when available.
• Redact API keys, passwords, and secured write values in exception messages and CLI output.

CLI

• Keep CLI output deterministic for tests.
• Support JSON output for automation.
• Load API keys from explicit flags or named environment variables. Do not read secrets implicitly during module import.

Tests

• Use pytest and pytest-asyncio.
• Use fake generated stubs or an in-process test gRPC server for unit tests.
• Keep live integration tests behind MXGATEWAY_INTEGRATION=1.