Python Development — Quanture Standards

Quick start

Always activate virtual environment before working:

python3 -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt

Code standards

• Python 3.10+ required
• Type hints on all functions
• Black formatter: black .
• Linting: ruff check .
• Tests: pytest tests/

from typing import Optional

def process_data(input: str, limit: Optional[int] = None) -> dict:
    """Brief docstring explaining what this does."""
    # implementation
    ...

Security rules

• Never hardcode credentials, tokens, or passwords
• Load secrets from environment variables: os.environ.get("SECRET_KEY")
• Validate and sanitize all external inputs
• Use subprocess.run([...], shell=False) — never shell=True with user input
• Log errors but never log sensitive data

Project structure

project/
├── src/
│   └── module/
├── tests/
├── requirements.txt
├── .env.example       # template without real values
└── README.md

Error handling

try:
    result = risky_operation()
except SpecificError as e:
    logger.error("Operation failed: %s", e)
    raise

Never use bare except: — always catch specific exceptions.

Database queries

Use parameterized queries always:

# GOOD
cursor.execute("SELECT * FROM users WHERE id = %s", (user_id,))

# NEVER — SQL injection risk
cursor.execute(f"SELECT * FROM users WHERE id = {user_id}")

Advanced reference

• APIs: See reference/apis.md
• Testing patterns: See reference/testing.md
• Common utilities: See reference/utils.md