Jamie-BitFlight $ARGUMENTS
Python Modernization Guide
The model applies modern Python 3.11+ patterns when writing or reviewing Python code.
Arguments
Instructions
If file paths provided:
- Read each file
- Identify legacy patterns
- Apply modern transformations from the reference guide
- Report changes made or recommended
If topic provided (e.g., "typing", "match-case"):
- Provide guidance on that specific topic
- Show before/after examples
If no arguments:
- Ask what code to review or what topic to explain
Quick Reference: Modern Patterns
Type Hints (PEP 585, 604)
# Legacy (NEVER use)
from typing import List, Dict, Optional, Union
# Modern (ALWAYS use)
items: list[str]
config: dict[str, int] | None
value: int | str
Walrus Operator (PEP 572)
# Legacy
data = fetch_data()
if data:
process(data)
# Modern
if data := fetch_data():
process(data)
Match-Case (PEP 634)
Use match-case when using elif. Use if/elif only for inequalities or boolean operators.
# Modern (for any elif pattern)
match status_code:
case 200:
return "OK"
case 404:
return "Not Found"
case _:
return "Unknown"
Self Type (PEP 673)
from typing import Self
class Builder:
def add(self, x: int) -> Self:
self.value += x
return self
Exception Notes (PEP 678)
except FileNotFoundError as e:
e.add_note(f"Attempted path: {path}")
raise
StrEnum (Python 3.11+)
from enum import StrEnum
class Status(StrEnum):
PENDING = "pending"
RUNNING = "running"
TOML Support (Python 3.11+)
import tomllib
from pathlib import Path
config = tomllib.load(Path("pyproject.toml").open("rb"))
Testing Patterns
ALWAYS use pytest-mock, NEVER unittest.mock:
# Legacy (NEVER use)
from unittest.mock import Mock, patch
# Modern (ALWAYS use)
from pytest_mock import MockerFixture
def test_feature(mocker: MockerFixture) -> None:
mock_func = mocker.patch("module.function", return_value=42)
Framework Patterns
Typer CLI
ALWAYS use Annotated syntax:
from typing import Annotated
import typer
@app.command()
def process(
input_file: Annotated[Path, typer.Argument(help="Input file")],
verbose: Annotated[bool, typer.Option("--verbose", "-v")] = False,
) -> None:
"""Process input file."""
pass
Rich Tables
Use explicit width control for production CLIs:
from rich.console import Console
from rich.table import Table
from rich.measure import Measurement
def _get_table_width(table: Table) -> int:
temp_console = Console(width=9999)
measurement = Measurement.get(temp_console, temp_console.options, table)
return int(measurement.maximum)
Core Principles
- Use Python 3.11+ as minimum baseline
- Leverage built-in generics (PEP 585) and pipe unions (PEP 604) exclusively
- Apply walrus operator to reduce line count
- Use match-case for elif patterns
- Implement comprehensive type hints with Protocol, TypeVar, TypeGuard
- Use Self type (PEP 673) for fluent APIs
- Follow Typer patterns with Annotated syntax for CLIs
- Use Rich for terminal output with proper width handling
- Write pytest tests with pytest-mock and AAA pattern
- Apply clean architecture with dependency injection