Constrained / Legacy Environments

Consult python3-core for standing defaults.

This skill is for CONFIRMED constraints only. Do not assume restrictions. Verify with the user first.

flowchart TD
    Start([Need Python CLI script]) --> Q1{Environment allows network access?}
    Q1 -->|Yes| UseTyper[Use python3-cli with Typer+Rich]
    Q1 -->|No| Q2{Restriction type confirmed?}
    Q2 -->|No| Stop[STOP — Verify with user first]
    Q2 -->|Yes| StdLib[Use stdlib-only patterns]

Required Behavior

• Preserve compatibility before applying modernization patterns
• Prefer stdlib solutions when dependency policy is restrictive
• Choose typing features valid for the project floor
• Make boundary wrappers explicit when Pydantic is unavailable
• Avoid recommending tools or syntax that exceed the project lane

Stdlib CLI

import argparse

def create_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(
        description="Tool description",
        formatter_class=argparse.RawDescriptionHelpFormatter,
    )
    return parser

Stdlib Logging

import logging
from pathlib import Path

def setup_logging(level: str = "INFO", log_file: Path | None = None) -> None:
    handlers: list[logging.Handler] = [logging.StreamHandler()]
    if log_file:
        handlers.append(logging.FileHandler(log_file))
    logging.basicConfig(
        level=getattr(logging, level.upper(), logging.INFO),
        format="%(asctime)s %(name)s %(levelname)s %(message)s",
        handlers=handlers,
    )

Stdlib Config

import json, tomllib
from pathlib import Path

def load_config(path: Path) -> dict[str, object]:
    ext = path.suffix.lower()
    if ext == ".json":
        return json.loads(path.read_text())
    if ext == ".toml":
        return tomllib.loads(path.read_text())
    raise ValueError(f"Unsupported config format: {ext}")

Shebang

Stdlib-only scripts use #!/usr/bin/env python3 (no PEP 723 metadata — nothing to declare).

References

• references/command-execution.md, references/type-safety-patterns.md, references/typing-strategy.md — stdlib patterns and compatibility guidance