# Justanesta Claude Code Resources Python API Development

> Python API Development

- Skill: `tomevault-io/justanesta-claude-code-resources-python-api-development` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/justanesta-claude-code-resources-python-api-development`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/justanesta-claude-code-resources-python-api-development/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/justanesta-claude-code-resources-python-api-development

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# Python API Development

Modern patterns for building production-ready APIs with FastAPI and Flask.

## Decision Matrix: FastAPI vs Flask

| Factor | FastAPI | Flask | Winner |
|--------|---------|-------|--------|
| **Performance** | High (async) | Moderate | FastAPI |
| **Auto docs** | Built-in (OpenAPI) | Manual | FastAPI |
| **Validation** | Pydantic (automatic) | Manual/extensions | FastAPI |
| **Learning curve** | Steeper | Gentler | Flask for beginners |
| **Async support** | Native | With extensions | FastAPI |

**General guidance**:
- **Use FastAPI when**: New projects, async needed, want auto-docs, type safety important
- **Use Flask when**: Simple apps, team knows Flask, sync-only fine, want simplicity

## FastAPI Patterns

### Basic API Structure

```python
from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float

@app.get("/")
def read_root():
    return {"message": "Hello World"}

@app.post("/items/")
def create_item(item: Item):
    return item
```

### Pydantic Models for Validation

```python
from pydantic import BaseModel, Field

class User(BaseModel):
    username: str = Field(..., min_length=3, max_length=50)
    email: str
    age: int = Field(..., ge=0, le=150)
```

See [pydantic-validation.md](references/pydantic-validation.md) for:
- Custom validators
- Model inheritance
- Nested models

### Dependency Injection

```python
from fastapi import Depends

def get_db():
    db = Database()
    try:
        yield db
    finally:
        db.close()

@app.get("/items/")
def read_items(db = Depends(get_db)):
    return db.get_items()
```

See [dependency-injection-patterns.md](references/dependency-injection-patterns.md) for:
- Class-based dependencies
- Dependency override (testing)
- Sub-dependencies

### Async Endpoints

```python
@app.get("/data/")
async def get_data():
    async with httpx.AsyncClient() as client:
        response = await client.get("https://api.example.com/data")
        return response.json()
```

See [async-api-patterns.md](references/async-api-patterns.md) for:
- When async helps
- Database async patterns
- Concurrent request handling

## Flask Patterns

### Basic Flask API

```python
from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route("/users/<int:user_id>")
def get_user(user_id):
    user = db.get_user(user_id)
    return jsonify(user)
```

See [flask-patterns.md](references/flask-patterns.md) for:
- Application factory pattern
- Flask extensions
- Request hooks

## API Design Best Practices

### RESTful Conventions

```python
GET    /api/users          # List users
POST   /api/users          # Create user
GET    /api/users/123      # Get user
PUT    /api/users/123      # Update user
DELETE /api/users/123      # Delete user
```

### Response Structure

```python
# Success
{"data": {...}, "meta": {"timestamp": "..."}}

# Error
{"error": {"code": "...", "message": "...", "details": [...]}}
```

## Authentication Patterns

See [authentication-patterns.md](references/authentication-patterns.md) for:
- JWT with FastAPI
- OAuth2 with FastAPI
- API keys
- Session-based (Flask)

## Anti-Patterns to Avoid

| Avoid | Use Instead |
|-------|-------------|
| Verbs in URLs (`/getUser`) | Nouns + HTTP methods (`GET /users`) |
| No validation | Pydantic models (FastAPI) |
| Catching all exceptions | Specific error handlers |

source: FastAPI docs, Flask docs, REST API best practices

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