[CHORE] Modernize Python syntax with pyupgrade (ruff UP rules)

## Summary Run `ruff check --fix --select UP` across the codebase to modernize Python syntax automatically. This is a low-risk, high-value cleanup that improves code consistency and readability. Suggested by @bblommers in #1838: > "Speaking of: running `ruff check --select UP` seems to be mostly f-strings violations, which could be fixed automatically using `ruff check --fix`. I would be happy to add that as part of this PR - but I would recommend running that against the entire codebase in a separate PR for that. It makes reviewing a lot easier!" ## What pyupgrade (UP) Does The `UP` rule set modernizes Python syntax to use newer, cleaner constructs. Key transformations include: ### String Formatting → f-strings ```python # Before (UP031, UP032) "Hello, %s" % name "Hello, {}".format(name) # After f"Hello, {name}" ``` ### Type Annotations → Modern Syntax ```python # Before (UP006, UP007) from typing import Dict, List, Optional, Union x: Optional[str] y: Union[int, str] z: Dict[str, List[int]] # After x: str | None y: int | str z: dict[str, list[int]] ``` ### Other Modernizations | Rule | Before | After | |------|--------|-------| | UP005 | `assertEquals()` | `assertEqual()` | | UP008 | `super(Foo, self)` | `super()` | | UP009 | `# -*- coding: utf-8 -*-` | (removed, UTF-8 is default) | | UP010 | `from __future__ import print_function` | (removed) | | UP015 | `open("f", "r")` | `open("f")` | | UP018 | `str("literal")` | `"literal"` | | UP025 | `"unicode"` encoding | (simplified) | | UP028 | `yield` in `for` loop | `yield from` | | UP034 | `(x,)` extraneous parens | `x,` | | UP035 | `typing.Dict` | `dict` | | UP036 | Version checks for old Python | (removed) | | UP038 | `isinstance(x, (A, B))` | `isinstance(x, A \| B)` | ## Implementation ### Step 1: Preview Changes ```bash # See what would change (dry run) ruff check --select UP src/autobahn/ ``` ### Step 2: Auto-fix ```bash # Apply fixes automatically ruff check --fix --select UP src/autobahn/ ``` ### Step 3: Manual Review Some changes may need manual attention: - Complex string formatting with many arguments - Edge cases in type annotations - Any changes that affect runtime behavior (rare but possible) ### Step 4: Run Tests ```bash just test cpy314 ``` ## Scope **In scope:** - All `.py` files in `src/autobahn/` - Automatic fixes via `ruff --fix` - Manual fixes for any remaining violations **Out of scope:** - Test files (can be done in follow-up) - Changes that would affect public API signatures - Any behavioral changes (this is purely syntactic) ## Why a Separate PR? As @bblommers noted, keeping this separate from typing work makes review much easier: 1. **Single concern** — only modernization, no new types 2. **Mechanical changes** — easy to verify correctness 3. **Clean diff** — reviewers can focus on unexpected changes 4. **Bisectable** — if issues arise, easy to identify source ## Acceptance Criteria - [ ] `ruff check --select UP src/autobahn/` reports zero violations - [ ] All tests pass (`just test cpy314`) - [ ] CI passes - [ ] No changes to public API behavior ## Assignee @bblommers has hinted at / offered to take this on — thank you, should you decide to invest time & work! ## Related - #1838 — Initial typing contribution (merged) - #1839 — Typed subset initiative (parent) - #1840 — Add ruff ANN checks to check-typing recipe ## References - [ruff pyupgrade (UP) rules](https://docs.astral.sh/ruff/rules/#pyupgrade-up) - [pyupgrade project](https://github.com/asottile/pyupgrade) ## Checklist - [x] I have searched existing issues to avoid duplicates - [x] I have described the problem clearly - [x] I have provided use cases - [x] I have considered alternatives - [x] I have assessed impact and breaking changes