# FastAPI decorators
[](https://pypi.org/project/fastapi-decorators/)
[](https://pypi.org/project/fastapi-decorators/)
[](https://pypi.org/project/fastapi-decorators/)
Create decorators that leverage FastAPI's `Depends()` and built-in dependencies, enabling you to inject dependencies directly into your decorators.
# Installation
```bash
pip install fastapi-decorators
```
# TL;DR
The library supplies the `depends()` decorator function which effectively allows you to add argument dependencies to your FastAPI endpoints.
For example, the following three endpoints have the same signature:
```python
# Using normal dependencies
@app.get("/items/{item_id}")
def read_item(item_id: int, _ = Depends(get_current_user)):
...
# Using add_dependency directly
@app.get("/items/{item_id}")
@depends(Depends(get_current_user))
def read_item(item_id: int):
...
# Using a custom decorator
def authorize():
def dependency(user = Depends(get_current_user)):
return user
return depends(Depends(dependency))
@app.get("/items/{item_id}")
@authorize()
def read_item(item_id: int):
...
```
# Usage examples
- [Using `depends()` directly](#using-depends-directly)
- [Logging decorator](#logging-decorator)
- [Authorization decorator](#authorization-decorator)
- [Custom Response Header decorator](#custom-response-header-decorator)
- [Rate Limiting decorator](#rate-limiting-decorator)
- [Caching decorator](#caching-decorator)
- [Error Handling decorator](#error-handling-decorator)
- [Combining Multiple decorators](#combining-multiple-decorators)
- [Dependency injection with parameters](#dependency-injection-with-parameters)
## Using `depends()` directly
If you prefer, you can use depends directly without creating a custom decorator:
```python
from fastapi_decorators import depends
from fastapi import Depends, Header
async def verify_api_key(x_api_key: str = Header(...)):
if x_api_key != "expected-api-key":
raise HTTPException(status_code=403, detail="Forbidden")
@app.get("/secure-data")
@depends(Depends(verify_api_key))
def get_secure_data():
...
```
## Logging decorator
Add a decorator to log incoming requests:
```python
from fastapi_decorators import depends
from fastapi import Request, Depends
def log_request():
def dependency(request: Request):
print(f"Received request: {request.method} {request.url}")
return depends(Depends(dependency))
@app.get("/items/{item_id}")
@log_request()
def read_item(item_id: int):
...
```
## Authorization decorator
Create a simple decorator that rejects unauthorized requests:
> The API docs will reflect the authentication requirement for this endpoint
> because of the added OAuth2 dependency.
```python
from fastapi_decorators import depends
from fastapi import Depends, HTTPException, Header
from fastapi.security import OAuth2PasswordBearer
from sqlalchemy.orm import Session
oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")
def authorize(*required_scopes: str):
def dependency(token: str = Depends(oauth2_scheme)):
# Your auth logic here
if not token:
raise HTTPException(status_code=401, detail="Unauthorized")
# Check scopes and permissions
pass
return depends(Depends(dependency))
@app.put("/users/{user_id}")
@authorize("users:write")
def update_user(*, user_id: int, user_update: UserUpdate):
...
```
## Custom Response Header decorator
Create a decorator to add custom headers to responses:
```python
from fastapi_decorators import depends
from fastapi import Response, Depends
def add_custom_header(name: str, value: str):
def dependency(response: Response):
response.headers[name] = value
return depends(Depends(dependency))
@app.get("/data")
@add_custom_header("X-Custom-Header", "MyValue")
def get_data():
...
```
## Rate Limiting decorator
Add rate limiting to your endpoints:
```python
from fastapi_decorators import depends
from fastapi import Depends, HTTPException, Request
from time import time
rate_limit_store = {}
def rate_limit(max_calls: int, period: int):
def dependency(ip_address: str = Depends(get_ip_address)):
# Simple rate limiting logic
now = time()
calls, last_reset = rate_limit_store.get(ip_address, (0, now))
if now - last_reset > period:
# Reset rate limit
calls = 0
last_reset = now
if calls >= max_calls:
raise HTTPException(status_code=429, detail="Too Many Requests")
calls += 1
rate_limit_store[ip_address] = (calls, last_reset)
return depends(Depends(dependency))
def get_ip_address(request: Request):
return request.client.host
@app.get("/limited-endpoint")
@rate_limit(max_calls=5, period=60)
def limited_endpoint():
...
```
## Caching decorator
Add caching to your endpoints:
```python
def get_cache() -> dict:
return {} # Use a real cache like Redis or Memcached
def cache_response(max_age: int = 5):
def decorator(func):
# Wrap the endpoint after adding the get_cache dependency
@depends(cache=Depends(get_cache))
@wraps(func)
def wrapper(*args, cache: dict, **kwargs):
key = func.__name__
if key in cache:
timestamp, data = cache[key]
if time() - timestamp < max_age:
# Cache hit
return data
# Cache miss - call the endpoint as usual
result = func(*args, **kwargs)
# Store the result in the cache
cache[key] = time(), result
return result
return wrapper
return decorator
@app.get("/cached-data")
@cache_response(max_age=10)
def get_cached_data():
...
```
## Error Handling decorator
Create a decorator to handle exceptions and return custom responses:
```python
from fastapi_decorators import depends
from fastapi import Depends, Response
def get_crash_log_storage() -> list:
return [] # Use a real storage like a database
def handle_errors():
def decorator(func):
# Wrap the endpoint after adding the crash_logs dependency
@depends(crash_logs = Depends(get_crash_log_storage))
@wraps(func)
def wrapper(*args, crash_logs: list, **kwargs):
try:
return func(*args, **kwargs)
except Exception as e:
# Log the error and return a custom response
crash_logs.append({ 'error': str(e), 'function': func.__name__ })
return JSONResponse(status_code=500, content={ "detail": str(e) })
return wrapper
return decorator
@app.get("/may-fail")
@handle_errors()
def may_fail_operation():
...
```
## Combining Multiple decorators
You can combine multiple decorators to compose complex behavior:
```python
@app.post("/submit")
@log_request()
@add_custom_header("X-Processed-By", "FastAPI")
@handle_errors()
def submit_data(data: DataModel):
...
```
## Dependency injection with parameters
You can pass parameters to your dependencies through closures:
```python
from fastapi_decorators import depends
from fastapi import Depends, HTTPException
def verify_role(required_role: str):
def dependency(current_user: User = Depends(get_current_user)):
if current_user.role != required_role:
raise HTTPException(status_code=403, detail="Forbidden")
return dependency
@app.get("/admin-area")
@depends(Depends(verify_role("admin")))
def admin_area():
...
```
# Credits
Inspired by solutions suggested by [@gocreating](https://github.com/gocreating) and [@dmontagu](https://github.com/dmontagu).
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"description": "# FastAPI decorators\n\n[](https://pypi.org/project/fastapi-decorators/)\n[](https://pypi.org/project/fastapi-decorators/)\n[](https://pypi.org/project/fastapi-decorators/)\n\nCreate decorators that leverage FastAPI's `Depends()` and built-in dependencies, enabling you to inject dependencies directly into your decorators.\n\n# Installation\n```bash\npip install fastapi-decorators\n```\n\n# TL;DR\nThe library supplies the `depends()` decorator function which effectively allows you to add argument dependencies to your FastAPI endpoints.\n\nFor example, the following three endpoints have the same signature:\n```python\n# Using normal dependencies\n@app.get(\"/items/{item_id}\")\ndef read_item(item_id: int, _ = Depends(get_current_user)):\n ...\n\n# Using add_dependency directly\n@app.get(\"/items/{item_id}\")\n@depends(Depends(get_current_user))\ndef read_item(item_id: int):\n ...\n\n# Using a custom decorator\ndef authorize():\n def dependency(user = Depends(get_current_user)):\n return user\n return depends(Depends(dependency))\n\n@app.get(\"/items/{item_id}\")\n@authorize()\ndef read_item(item_id: int):\n ...\n```\n\n# Usage examples\n\n- [Using `depends()` directly](#using-depends-directly)\n- [Logging decorator](#logging-decorator)\n- [Authorization decorator](#authorization-decorator)\n- [Custom Response Header decorator](#custom-response-header-decorator)\n- [Rate Limiting decorator](#rate-limiting-decorator)\n- [Caching decorator](#caching-decorator)\n- [Error Handling decorator](#error-handling-decorator)\n- [Combining Multiple decorators](#combining-multiple-decorators)\n- [Dependency injection with parameters](#dependency-injection-with-parameters)\n\n## Using `depends()` directly\nIf you prefer, you can use depends directly without creating a custom decorator:\n\n```python\nfrom fastapi_decorators import depends\nfrom fastapi import Depends, Header\n\nasync def verify_api_key(x_api_key: str = Header(...)):\n if x_api_key != \"expected-api-key\":\n raise HTTPException(status_code=403, detail=\"Forbidden\")\n\n@app.get(\"/secure-data\")\n@depends(Depends(verify_api_key))\ndef get_secure_data():\n ...\n\n```\n\n## Logging decorator\nAdd a decorator to log incoming requests:\n\n```python\nfrom fastapi_decorators import depends\nfrom fastapi import Request, Depends\n\ndef log_request():\n def dependency(request: Request):\n print(f\"Received request: {request.method} {request.url}\")\n return depends(Depends(dependency))\n\n@app.get(\"/items/{item_id}\")\n@log_request()\ndef read_item(item_id: int):\n ...\n\n```\n\n## Authorization decorator\nCreate a simple decorator that rejects unauthorized requests:\n> The API docs will reflect the authentication requirement for this endpoint\n> because of the added OAuth2 dependency.\n\n```python\nfrom fastapi_decorators import depends\nfrom fastapi import Depends, HTTPException, Header\nfrom fastapi.security import OAuth2PasswordBearer\nfrom sqlalchemy.orm import Session\n\noauth2_scheme = OAuth2PasswordBearer(tokenUrl=\"token\")\n\ndef authorize(*required_scopes: str):\n def dependency(token: str = Depends(oauth2_scheme)):\n # Your auth logic here\n if not token:\n raise HTTPException(status_code=401, detail=\"Unauthorized\")\n\n # Check scopes and permissions\n pass\n return depends(Depends(dependency))\n\n\n@app.put(\"/users/{user_id}\")\n@authorize(\"users:write\")\ndef update_user(*, user_id: int, user_update: UserUpdate):\n ...\n\n```\n\n## Custom Response Header decorator\nCreate a decorator to add custom headers to responses:\n\n```python\nfrom fastapi_decorators import depends\nfrom fastapi import Response, Depends\n\ndef add_custom_header(name: str, value: str):\n def dependency(response: Response):\n response.headers[name] = value\n return depends(Depends(dependency))\n\n@app.get(\"/data\")\n@add_custom_header(\"X-Custom-Header\", \"MyValue\")\ndef get_data():\n ...\n\n```\n\n## Rate Limiting decorator\nAdd rate limiting to your endpoints:\n\n```python\nfrom fastapi_decorators import depends\nfrom fastapi import Depends, HTTPException, Request\nfrom time import time\n\nrate_limit_store = {}\n\ndef rate_limit(max_calls: int, period: int):\n def dependency(ip_address: str = Depends(get_ip_address)):\n # Simple rate limiting logic\n now = time()\n calls, last_reset = rate_limit_store.get(ip_address, (0, now))\n if now - last_reset > period:\n # Reset rate limit\n calls = 0\n last_reset = now\n if calls >= max_calls:\n raise HTTPException(status_code=429, detail=\"Too Many Requests\")\n calls += 1\n rate_limit_store[ip_address] = (calls, last_reset)\n return depends(Depends(dependency))\n\ndef get_ip_address(request: Request):\n return request.client.host\n\n@app.get(\"/limited-endpoint\")\n@rate_limit(max_calls=5, period=60)\ndef limited_endpoint():\n ...\n\n```\n\n## Caching decorator\nAdd caching to your endpoints:\n\n```python\ndef get_cache() -> dict:\n return {} # Use a real cache like Redis or Memcached\n\ndef cache_response(max_age: int = 5):\n def decorator(func):\n\n # Wrap the endpoint after adding the get_cache dependency\n @depends(cache=Depends(get_cache))\n @wraps(func)\n def wrapper(*args, cache: dict, **kwargs):\n key = func.__name__\n\n if key in cache:\n timestamp, data = cache[key]\n if time() - timestamp < max_age:\n # Cache hit\n return data\n\n # Cache miss - call the endpoint as usual\n result = func(*args, **kwargs)\n\n # Store the result in the cache\n cache[key] = time(), result\n return result\n \n return wrapper\n return decorator\n\n@app.get(\"/cached-data\")\n@cache_response(max_age=10)\ndef get_cached_data():\n ...\n```\n\n## Error Handling decorator\nCreate a decorator to handle exceptions and return custom responses:\n\n```python\nfrom fastapi_decorators import depends\nfrom fastapi import Depends, Response\n\ndef get_crash_log_storage() -> list:\n return [] # Use a real storage like a database\n\ndef handle_errors():\n def decorator(func):\n\n # Wrap the endpoint after adding the crash_logs dependency\n @depends(crash_logs = Depends(get_crash_log_storage))\n @wraps(func)\n def wrapper(*args, crash_logs: list, **kwargs):\n try:\n return func(*args, **kwargs)\n except Exception as e:\n # Log the error and return a custom response\n crash_logs.append({ 'error': str(e), 'function': func.__name__ })\n return JSONResponse(status_code=500, content={ \"detail\": str(e) })\n \n return wrapper\n return decorator\n\n@app.get(\"/may-fail\")\n@handle_errors()\ndef may_fail_operation():\n ...\n\n```\n\n## Combining Multiple decorators\nYou can combine multiple decorators to compose complex behavior:\n\n```python\n@app.post(\"/submit\")\n@log_request()\n@add_custom_header(\"X-Processed-By\", \"FastAPI\")\n@handle_errors()\ndef submit_data(data: DataModel):\n ...\n\n```\n\n## Dependency injection with parameters\nYou can pass parameters to your dependencies through closures:\n\n```python\nfrom fastapi_decorators import depends\nfrom fastapi import Depends, HTTPException\n\ndef verify_role(required_role: str):\n def dependency(current_user: User = Depends(get_current_user)):\n if current_user.role != required_role:\n raise HTTPException(status_code=403, detail=\"Forbidden\")\n return dependency\n\n@app.get(\"/admin-area\")\n@depends(Depends(verify_role(\"admin\")))\ndef admin_area():\n ...\n\n```\n\n# Credits\nInspired by solutions suggested by [@gocreating](https://github.com/gocreating) and [@dmontagu](https://github.com/dmontagu).\n",
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