chocs 0.1.1

Lightweight and powerful layer for building rest applications based on wsgi servers.

Chocs

Chocs is a modern HTTP framework for WSGI compatible servers. Chocs aims to be small, expressive, and robust. It provides an elegant API for writing fault-proof, extensible microservices.

Features

• Elegant and easy API
• No additional bloat like built-in template engines, session handlers, etc.
• Compatible with all WSGI servers
• Loosely coupled components which can be used separately
• Multipart body parsing
• Graceful error handling
• HTTP middleware support
• Fast routing

Installation

pip install chocs

Usage

Quick start

from chocs import HttpRequest, HttpResponse, router, serve

@router.get("/hello/{name}")
def hello(request: HttpRequest) -> HttpResponse:
    return HttpResponse(f"Hello {request.attributes['name']}!")

serve()

Keep in mind that the serve() function is using the bjoern package, so make sure you included it in your project dependencies before using it. You are able to use any WSGI compatible server.

Running application with Gunicorn (or any other WSGI server)

# myapp.py
from chocs import Application, HttpRequest, HttpResponse, router

@router.get("/hello/{name}*")
def hello(request: HttpRequest) -> HttpResponse:
    return HttpResponse(f"Hello {request.attributes['name']}!")

app = Application(router)

gunicorn -w 4 myapp:app

Routing

Chocs is shipped with a built-in routing module. The easiest way to utilise chocs' routing is to use chocs.router object. chocs.router is an instance of the module's internal class chocs.chocs.ApplicationRouter, which provides a simple API where each function is a decorator corresponding to an HTTP method.

from chocs import router, HttpResponse, HttpRequest

@router.get("/hello")
def hello(req: HttpRequest) -> HttpResponse:
    ...

The above example will assign the hello function to handle a GET /hello request.

Available methods:

• delete
• get
• head
• options
• patch
• post
• put
• trace

Parametrized routes

Routes can contain parameterised parts. Parameters must be enclosed within { and }.

from chocs import router

@router.get("/pet/{id}")
def hello():
    ...

Will match the following URIs:

• /pet/1
• /pet/abc
• /pet/abc1

Advanced matching can be achieved by passing a regex to the function. Consider the following example:

from chocs import router

@router.get("/pet/{id}", id=r"\d+")
def hello():
    ...

This restricts the id parameter to accept only digits, so /pet/abc and /pet/abc1 will no longer match route's pattern.

Wildcard routes

Asterisks (*) can be used in the route's pattern to match any possible combination. Keep in mind that routes which do not contain wildcards are prioritised over routes with wildcards.

from chocs import router

@router.get("/pet/*", id)
def hello():
    ...

The above example will match following URIs:

• /pet/a
• /pet/a/b/c
• /pet/12jd/fds

Defining and using a custom middleware

Middleware are functions or classes that inherit chocs.middleware.Middleware. Middlewares have access to the request object and the next function is used to control middleware stack flow. Successful middleware execution should call the next function (which accepts a chocs.HttpRequest instance and returns chocs.HttpReponse) and return a valid chocs.HttpResponse instance.

Middlewares can perform various tasks:

• Making changes in request/response objects ending
• Validating input data
• Authenticating users
• End request-response cycle
• Connecting to external data sources

Middlewares are different to functions decorated by router.* decorators as they are executed every time a request happens and they are not bound to the URI.

from chocs import HttpRequest, HttpResponse, serve
from chocs.middleware import MiddlewareHandler

def my_custom_middleware(request: HttpRequest, next: MiddlewareHandler) -> HttpResponse:
    name = request.query_string.get("name", "John")
    return HttpResponse(body=f"Hello {name}")

serve(my_custom_middleware)

Request

chocs.Request object is an abstraction around WSGI's environment and wsgi.input data with handy interface to ease everyday work.

chocs.Request.headers:dict

Keeps parsed headers in dict-like object.

chocs.Request.body:io.BytesIO

Raw body data

Request.parsed_body:chocs.message.RequestBody

Depending on the content type it could be one of the following:

• chocs.message.FormBody
• chocs.message.JsonBody
• chocs.message.MultiPartBody

chocs.Request.cookies:typing.List[chocs.cookies.Cookie]

Request's cookies

chocs.Request.method:chocs.HttpMethod

The request's method

chocs.Request.uri:str

The request's URI

chocs.Request.query_string:chocs.QueryString

A dict like object with parsed query string with JSON forms support

chocs.Request.attributes:dict

Matched route attributes, for example when /users/john matches the /users/{name} route, attributes will contain a name key with a value of john

Response

chocs.Response object is a part of request-response flow and it is required to be returned by all functions decorated with router.* method. Instance of the response class is recognised by chocs.Application and used to generate real response served to your clients.

chocs.Response.body: io.BytesIO

Body served to server's clients.

chocs.Response.status_code: Union[chocs.HttpStatus, int]

Valid response code, instance of chocs.HttpStatus enum can be used or just a status code's number.

chocs.Request.headers (read-only)

Keeps parsed headers in dict-like object. This property is read-only and can be set only on object instantiation.

chocs.Response.cookies:typing.List[chocs.cookies.Cookie]

Response's cookies

chocs.Response.write(body: Union[bytes, str, bytearray])

Write bytes to response body

chocs.Response.close()

Makes body non-writable.

chocs.Response.writable: bool

Indicates whether response's body is writable.

Working with cookies

chocs.CookieJar object takes care of cookie handling. It can be accessed in dict-like manner, when item is requested, instance of chocs.Cookie is returned to user.

Cookies can be set either by passing string value to the chocs.CookieJar's key, or by calling chocs.CookieJar.append method which accepts instance of chocs.Cookie.

Reading client cookies

Cookies can be easily accessed from chocs.Request.cookies object which is injected as a parameter to each function registered as route handler. Consider the following example:

from chocs import HttpRequest, HttpResponse, serve, router


@router.get("/cookies")
def read_cookies(request: HttpRequest) -> HttpResponse:

    message = "Hello"
    if "user_name" in request.cookies:
        message += f", {str(request.cookies['user_name'])}"
    message += "!"

    return HttpResponse(body=message)

serve()

Setting cookies

from chocs import HttpRequest, HttpResponse, serve, router, Cookie
from datetime import datetime


@router.get("/cookies")
def read_cookies(request: HttpRequest) -> HttpResponse:
    response = HttpResponse(body="Hi! I have baked some cookies for ya!")
    response.cookies['simple-cookie'] = "Simple cookie for simple people"
    response.cookies.append(Cookie("advanced-cookie", "This cookie will expire in 2021-01-01", expires=datetime(2021, 1, 1)))
    return response

serve()