Python Coding Standards Skill

Python Coding Standards

Mandatory Metadata

Every function or class you create or modify must include this header comment:

# Created by [Model_Name] | YYYY-MM-DD
# Example: # Created by GPT-5.5 | 2026-07-04

For modifications to existing functions/classes:

# Modified by [Model_Name] | YYYY-MM-DD
# Example: # Modified by Claude-Sonnet-4.8 | 2026-07-04

Use the current model name from context and today's date.

Syntax & Style

Quotes

Use double quotes (") in all cases.
- Good: x += "."
- Bad: x += '.'

String Formatting

Use f-strings for interpolation (not % or .format()).
- Good: f"Hello, {name}!"
- Bad: "Hello, {}!".format(name) or "Hello, %s" % name

SQL

Always use multi-line triple-quoted strings for SQL queries.

Readability

Prioritize readable code over clever/compact one-liners.
Keep vertical spacing compact — no excessive blank lines.

Type Hints

Add type hints to new functions you write (not required when modifying existing code without type hints).
```
def user_get(user_id: int) -> dict:
```

Error Handling

Use specific exception types — avoid bare except:.

Log errors with context before re-raising or returning.

try:
    result = file_read(path)
except FileNotFoundError as e:
    logger.error(f"File not found: {path} — {e}")
    raise

Docstrings

Add a one-line docstring to every new public function or class.

Use triple double-quotes.

def user_sync(folders: list) -> bool:
    """Sync skill directories across all provided folder paths."""

Flask-Specific Patterns

Route Organization

Keep route handlers thin — delegate logic to utility functions.
Group related routes into blueprints (blueprints/ folder).
Route naming: use domain-first (e.g., /user/edit or /user_edit, not /edit_user).

Error Handlers

@app.errorhandler(404)
def error_not_found(e):
    return jsonify({"error": "Not found"}), 404

Response Pattern

Use jsonify() for API responses; set explicit status codes.

Jinja2-Specific Patterns

Template Inheritance

All page templates should extend a base layout:

{% extends "layout.jinja" %}
{% block content %}
  {# page content here #}
{% endblock %}

Variable Safety

Use the | default() filter when a variable might be undefined:
```
{{ user.name | default("Guest") }}
```

Logic in Templates

Keep logic minimal in templates — complex logic belongs in Python, not Jinja.
Use {% set %} for local variables rather than inline expressions when readability suffers.

Testing (pytest)

Read skill-local guidance only when .kilocode/skills/coding-python/AGENTS.md is confirmed to exist; otherwise use root AGENTS.md for project-specific Python, Flask, Jinja, and test paths.
Test files generally follow test_[module_name].py naming.
Each test function name describes what it verifies: test_user_sync_creates_backup.
Use tmp_path fixture for file system tests — never write to real project paths.
Confirm a test doesn't already exist before writing a new one.

Agent Skills: Python Coding Standards

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