This section includes notes for using webargs with specific web frameworks.
Flask support is available via the webargs.flaskparser module.
When using the use_args decorator, the arguments dictionary will be before any URL variable parameters.
from webargs import fields
from webargs.flaskparser import use_args
@app.route('/user/<int:uid>')
@use_args({'per_page': fields.Int()})
def user_detail(args, uid):
return ('The user page for user {uid}, '
'showing {per_page} posts.').format(uid=uid,
per_page=args['per_page'])
Webargs uses Flask’s abort function to raise an HTTPException when a validation error occurs. If you use the Flask.errorhandler method to handle errors, you can access validation messages from the data attribute of an error.
Here is an example error handler that returns validation messages to the client as JSON.
from flask import jsonify
@app.errorhandler(422)
def handle_unprocessable_entity(err):
# webargs attaches additional metadata to the `data` attribute
data = getattr(err, 'data')
if data:
# Get validations from the ValidationError object
messages = data['exc'].messages
else:
messages = ['Invalid request']
return jsonify({
'messages': messages,
}), 422
The FlaskParser supports parsing values from a request’s view_args.
from webargs.flaskparser import use_args
@app.route('/greeting/<name>/')
@use_args({'name': fields.Str(location='view_args')})
def greeting(args, **kwargs):
return 'Hello {}'.format(args['name'])
Django support is available via the webargs.djangoparser module.
Webargs can parse Django request arguments in both function-based and class-based views.
When using the use_args decorator, the arguments dictionary will positioned after the request argument.
Function-based Views
from django.http import HttpResponse
from webargs import Arg
from webargs.djangoparser import use_args
account_args = {
'username': fields.Str(required=True),
'password': fields.Str(required=True),
}
@use_args(account_args)
def login_user(request, args):
if request.method == 'POST':
login(args['username'], args['password'])
return HttpResponse('Login page')
Class-based Views
from django.views.generic import View
from django.shortcuts import render_to_response
from webargs import fields
from webargs.djangoparser import use_args
blog_args = {
'title': fields.Str(),
'author': fields.Str(),
}
class BlogPostView(View):
@use_args(blog_args)
def get(self, request, args):
blog_post = Post.objects.get(title__iexact=args['title'],
author=args['author'])
return render_to_response('post_template.html',
{'post': blog_post})
The DjangoParser does not override handle_error, so your Django views are responsible for catching any ValidationErrors raised by the parser and returning the appropriate HTTPResponse.
from django.http import JsonResponse
from webargs import fields, ValidationError
argmap = {
'name': fields.Str(required=True)
}
def index(request):
try:
args = parser.parse(argmap, request)
except ValidationError as err:
return JsonResponse(err.messages, status=err.status_code)
return JsonResponse({'message': 'Hello {name}'.format(name=name)})
Tornado argument parsing is available via the webargs.tornadoparser module.
The webargs.tornadoparser.TornadoParser parses arguments from a tornado.httpserver.HTTPRequest object. The TornadoParser can be used directly, or you can decorate handler methods with use_args or use_kwargs.
import tornado.ioloop
import tornado.web
from webargs import fields
from webargs.tornadoparser import parser
class HelloHandler(tornado.web.RequestHandler):
hello_args = {
'name': fields.Str()
}
def post(self, id):
reqargs = parser.parse(self.hello_args, self.request)
response = {
'message': 'Hello {}'.format(reqargs['name'])
}
self.write(response)
application = tornado.web.Application([
(r"/hello/([0-9]+)", HelloHandler),
], debug=True)
if __name__ == "__main__":
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()
When using the use_args decorator, the decorated method will have the dictionary of parsed arguments passed as a positional argument after self and any regex match groups from the URL spec.
from webargs import fields
from webargs.tornadoparser import use_args
class HelloHandler(tornado.web.RequestHandler):
@use_args({'name': fields.Str()})
def post(self, id, reqargs):
response = {
'message': 'Hello {}'.format(reqargs['name'])
}
self.write(response)
application = tornado.web.Application([
(r"/hello/([0-9]+)", HelloHandler),
], debug=True)
As with the other parser modules, use_kwargs will add keyword arguments to the view callable.
A HTTPError will be raised in the event of a validation error. Your RequestHandlers are responsible for handling these errors.
Here is how you could write the error messages to a JSON response.
from tornado.web import RequestHandler
class MyRequestHandler(RequestHandler):
def write_error(self, status_code, **kwargs):
"""Write errors as JSON."""
self.set_header('Content-Type', 'application/json')
if 'exc_info' in kwargs:
etype, value, traceback = kwargs['exc_info']
if hasattr(value, 'messages'):
self.write({'errors': value.messages})
self.finish()
Pyramid support is available via the webargs.pyramidparser module.
When using the use_args decorator on a view callable, the arguments dictionary will be positioned after the request argument.
from pyramid.response import Response
from webargs import fields
from webargs.pyramidparser import use_args
@use_args({'per_page': fields.Int()})
def user_detail(request, args):
return Response('The user page for user {uid}, '
'showing {per_page} posts.').format(uid=uid,
per_page=args['per_page']))
As with the other parser modules, use_kwargs will add keyword arguments to the view callable.
The PyramidParser supports parsing values from a request’s matchdict.
from pyramid.response import Response
from webargs.pyramidparser import use_args
@parser.use_args({'mymatch': fields.Int()}, locations=('matchdict',))
def matched(request, args):
return Response('The value for mymatch is {}'.format(args['mymatch'])))
Falcon support is available via the webargs.falconparser module.
When using the use_args decorator on a resource method, the arguments dictionary will be positioned directly after the request and response arguments.
import falcon
from webargs import fields
from webargs.falconparser import use_args
class BlogResource:
request_args = {
'title': fields.Str(required=True)
}
@use_args(request_args)
def on_post(self, req, resp, args, post_id):
content = args['title']
# ...
api = application = falcon.API()
api.add_route('/blogs/{post_id}')
As with the other parser modules, use_kwargs will add keyword arguments to your resource methods.
You can easily implement hooks by using parser.parse directly.
import falcon
from webargs import fields
from webargs.falconparser import parser
def add_args(argmap, **kwargs):
def hook(req, resp, params):
parsed_args = parser.parse(argmap, req=req, **kwargs)
req.context['args'] = parsed_args
return hook
@falcon.before(add_args({'page': fields.Int(location='query')}))
class AuthorResource:
def on_get(self, req, resp):
args = req.context['args']
page = args.get('page')
# ...
aiohttp support is available via the webargs.aiohttpparser module.
The parse method of AIOHTTPParser is a coroutine.
import asyncio
from aiohttp import web
from webargs import fields
from webargs.aiohttpparser import parser
handler_args = {
'name': fields.Str(missing='World')
}
@asyncio.coroutine
def handler(request):
args = yield from parser.parse(handler_args, request)
return web.Response(
body='Hello, {}'.format(args['name']).encode('utf-8')
)
When using the use_args decorator on a handler, the parsed arguments dictionary will be the last positional argument.
import asyncio
from aiohttp import web
from webargs import fields
from webargs.aiohttpparser import use_args
@asyncio.coroutine
@use_args({'content': fields.Str(required=True)})
def create_comment(request, args):
content = args['content']
# ...
app = web.Application()
app.router.add_route('POST', '/comments/', create_comment)
As with the other parser modules, use_kwargs will add keyword arguments to your resource methods.
The use_args and use_kwargs decorators will not work with async def coroutines. You must either use a generator-based coroutine decorated with asyncio.coroutine or use parser.parse.
from aiohttp import web
from webargs import fields
hello_args = {
'name': fields.Str(missing='World')
}
# YES
from webargs.aiohttpparser import parser
async def hello(request):
args = await parser.parse(hello_args, request)
return web.Response(
body='Hello, {}'.format(name).encode('utf-8')
)
# YES
import asyncio
from webargs.aiohttpparser import use_kwargs
@asyncio.coroutine
@use_kwargs(hello_args)
def hello(request, name):
return web.Response(
body='Hello, {}'.format(name).encode('utf-8')
)
# NO: use_args and use_kwargs are incompatible with async def
@use_kwargs(hello_args)
async def hello(request, name):
return web.Response(
body='Hello, {}'.format(name).encode('utf-8')
)
The AIOHTTPParser supports parsing values from a request’s match_info.
from aiohttp import web
from webargs.aiohttpparser import use_args
@parser.use_args({'slug': fields.Str(location='match_info')})
def article_detail(request, args):
return web.Response(
body='Slug: {}'.format(args['slug']).encode('utf-8')
)
app = web.Application()
app.router.add_route('GET', '/articles/{slug}', article_detail)