init: common-skills v1

skills/python/SKILL.md

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+---
+name: python-skill
+description: Python coding best practices and patterns. Use when writing, reviewing, or debugging Python code.
+---
+
+# Python Skill
+
+## Type Hints (Python 3.10+)
+
+```python
+# Bad
+def process(data, callback):
+    return callback(data)
+
+# Good
+from typing import Callable
+
+def process(data: dict, callback: Callable[[dict], str]) -> str:
+    return callback(data)
+```
+
+## Dataclasses Over Plain Dicts
+
+```python
+from dataclasses import dataclass
+
+@dataclass
+class GameFrame:
+    timestamp: float
+    objects: list[str]
+    confidence: float = 1.0
+```
+
+## Context Managers for Resources
+
+```python
+# Bad
+f = open("log.txt")
+data = f.read()
+f.close()
+
+# Good
+with open("log.txt") as f:
+    data = f.read()
+```
+
+## List Comprehensions vs Loops
+
+```python
+# Prefer comprehension for simple transforms
+enemies = [obj for obj in objects if obj.type == "enemy"]
+
+# Use loop when logic is complex (>2 conditions)
+results = []
+for obj in objects:
+    if obj.type == "enemy" and obj.visible and obj.distance < 100:
+        results.append(obj.position)
+```
+
+## Error Handling
+```python
+# Be specific — never catch bare Exception silently
+try:
+    frame = capture_screen()
+except ScreenCaptureError as e:
+    logger.error("Screen capture failed: %s", e)
+    raise
+```