Use Python for data work and as a second server language

Cost

Open source. PSF licence, free to use and ship in any project.

How to do it

Python passes all five tests. Python 3.0 shipped in December 2008. Python 3.15 shipped on 9 October 2026, and 3.14 gets fixes until October 2027 and security fixes until October 2030. In the Stack Overflow Developer Survey 2025, 57.9% of developers used it. It uses the PSF licence, which the OSI approves. Start new projects on 3.14 and move to 3.15 in April 2027, once agents know it. Choose something else when the app has a large browser front end, where TypeScript lets one language cover both ends. Check its types, as Use Pyright to check Python types says.

Examples

Using these examples: they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

TOML example

[project]
name = "bookings-api"
version = "1.0.0"
requires-python = ">=3.14,<3.15"

Python example

from dataclasses import dataclass
from datetime import datetime

@dataclass(frozen=True)
class Booking:
    id: str
    starts_at: datetime
    seats: int

def total_seats(bookings: list[Booking]) -> int:
    return sum(booking.seats for booking in bookings)

How to check

python3 --version prints 3.14 or 3.15. requires-python in pyproject.toml names the same version. No server runs 3.10 or older.

Sources

• Status of Python versions
• Python downloads

Related rules

• Use Pyright to check Python types in Software choices