NetworkSec - Fast API

ref:

• https://github.com/tiangolo/fastapi/blob/master/README.md
• https://fastapi.tiangolo.com/tutorial/

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NetworkSec - Fast API

FastAPI framework, high performance, easy to learn, fast to code, ready for production

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Documentation: https://fastapi.tiangolo.com

Source Code: https://github.com/tiangolo/fastapi

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Overall

FastAPI is a modern, fast (high-performance), web framework for building APIs with Python 3.7+ based on standard Python type hints.

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Requirements

Python 3.7+

FastAPI stands on the shoulders of giants:

• Starlette for the web parts.
• Pydantic for the data parts.

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Installation

$ pip install fastapi

You will also need an ASGI server, for production such as Uvicorn or Hypercorn.

$ pip install "uvicorn[standard]"

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Example

Create it

• Create a file main.py with:

from typing import Union
from fastapi import FastAPI

app = FastAPI()

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

@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}

Or use async def...

If your code uses async / await, use async def:

from typing import Union

from fastapi import FastAPI

app = FastAPI()

# https://127.0.0.1:8000/
@app.get("/")
def read_root():
    return {"Hello": "World"}

# https://127.0.0.1:8000/items/5?q=somequery.
@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}

Note:

If you don’t know, check the “In a hurry?” section about async and await in the docs.

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Run it

Run the server with:

$ uvicorn main:app --reload

INFO:     Uvicorn running on https://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     Started reloader process [28720]
INFO:     Started server process [28722]
INFO:     Waiting for application startup.
INFO:     Application startup complete.

About the command uvicorn main:app --reload...

The command uvicorn main:app refers to:

• main: the file main.py (the Python “module”).
• app: the object created inside of main.py with the line app = FastAPI().
• --reload: make the server restart after code changes. Only do this for development.

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Check it

Open your browser at https://127.0.0.1:8000/items/5?q=somequery.

You will see the JSON response as:

{"item_id": 5, "q": "somequery"}

You already created an API that:

• Receives HTTP requests in the paths / and /items/{item_id}.
• Both paths take GET operations (HTTP methods).
• The path /items/{item_id} has a path parameter item_id that should be an int.
• The path /items/{item_id} has an optional str query parameter q.

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API docs

Interactive API docs

https://127.0.0.1:8000/docs

• automatic interactive API documentation (provided by Swagger UI):

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Alternative API docs

https://127.0.0.1:8000/redoc

• alternative automatic documentation (provided by ReDoc):

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Example upgrade

Now modify the file main.py to receive a body from a PUT request.

Declare the body using standard Python types, thanks to Pydantic.

from typing import Union
from fastapi import FastAPI
from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel):
    name: str
    price: float
    is_offer: Union[bool, None] = None

# https://127.0.0.1:8000/
@app.get("/")
def read_root():
    return {"Hello": "World"}

# https://127.0.0.1:8000/items/5?q=somequery.
@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}

@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):
    return {"item_name": item.name, "item_id": item_id}

The server should reload automatically (because you added --reload to the uvicorn command above).

FastAPI will:

• Validate that item_id in the path for GET and PUT requests.
• Validate that item_id is of type int for GET and PUT requests.
  • If it is not, the client will see a useful, clear error.
• Check if there is an optional query parameter named q for GET requests.
  • As the q parameter is declared with = None, it is optional.
  • Without the None it would be required (as is the body in the case with PUT).
• For PUT requests to /items/{item_id}, Read the body as JSON:
  • Check that it has a required attribute name that should be a str.
  • Check that it has a required attribute price that has to be a float.
  • Check that it has an optional attribute is_offer, that should be a bool, if present.
  • All this would also work for deeply nested JSON objects.

• Convert from and to JSON automatically.

• Document everything with OpenAPI, that can be used by:
  • Interactive documentation systems.
  • Automatic client code generation systems, for many languages.
• Provide 2 interactive documentation web interfaces directly.

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Interactive API docs upgrade

https://127.0.0.1:8000/docs

• The interactive API documentation will be automatically updated, including the new body:

• “Try it out”: fill the parameters and directly interact with the API:

• “Execute”: communicate with your API, send the parameters, get the results and show them on the screen:

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Alternative API docs upgrade

https://127.0.0.1:8000/redoc

• The alternative documentation will also reflect the new query parameter and body:

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command

For example, for an int:

item_id: int

or for a more complex Item model:

item: Item

…and with that single declaration you get:

• Editor support, including:
  • Completion.
  • Type checks.
• Validation of data:
  • Automatic and clear errors when the data is invalid.
  • Validation even for deeply nested JSON objects.
• Conversion of input data: coming from the network to Python data and types. Reading from:
  • JSON.
  • Path parameters.
  • Query parameters.
  • Cookies.
  • Headers.
  • Forms.
  • Files.
• Conversion of output data: converting from Python data and types to network data (as JSON):
  • Convert Python types (str, int, float, bool, list, etc).
  • datetime objects.
  • UUID objects.
  • Database models.
  • …and many more.
• Automatic interactive API documentation, including 2 alternative user interfaces:
  • Swagger UI.
  • ReDoc.