.. _reqparse: Request Parsing =============== .. warning :: The whole request parser part of Flask-RESTful is slated for removal and will be replaced by documentation on how to integrate with other packages that do the input/output stuff better (such as `marshmallow `_). This means that it will be maintained until 2.0 but consider it deprecated. Don't worry, if you have code using that now and wish to continue doing so, it's not going to go away any time too soon. .. currentmodule:: flask_restful Flask-RESTful's request parsing interface, :mod:`reqparse`, is modeled after the `argparse `_ interface. It's designed to provide simple and uniform access to any variable on the :class:`flask.request` object in Flask. Basic Arguments --------------- Here's a simple example of the request parser. It looks for two arguments in the :attr:`flask.Request.values` dict: an integer and a string :: from flask_restful import reqparse parser = reqparse.RequestParser() parser.add_argument('rate', type=int, help='Rate cannot be converted') parser.add_argument('name') args = parser.parse_args() .. note :: The default argument type is a unicode string. This will be ``str`` in python3 and ``unicode`` in python2. If you specify the ``help`` value, it will be rendered as the error message when a type error is raised while parsing it. If you do not specify a help message, the default behavior is to return the message from the type error itself. See :ref:`error-messages` for more details. By default, arguments are **not** required. Also, arguments supplied in the request that are not part of the RequestParser will be ignored. Also note: Arguments declared in your request parser but not set in the request itself will default to ``None``. Required Arguments ------------------ To require a value be passed for an argument, just add ``required=True`` to the call to :meth:`~reqparse.RequestParser.add_argument`. :: parser.add_argument('name', required=True, help="Name cannot be blank!") Multiple Values & Lists ----------------------- If you want to accept multiple values for a key as a list, you can pass ``action='append'`` :: parser.add_argument('name', action='append') This will let you make queries like :: curl http://api.example.com -d "name=bob" -d "name=sue" -d "name=joe" And your args will look like this :: args = parser.parse_args() args['name'] # ['bob', 'sue', 'joe'] Other Destinations ------------------ If for some reason you'd like your argument stored under a different name once it's parsed, you can use the ``dest`` keyword argument. :: parser.add_argument('name', dest='public_name') args = parser.parse_args() args['public_name'] Argument Locations ------------------ By default, the :class:`~reqparse.RequestParser` tries to parse values from :attr:`flask.Request.values`, and :attr:`flask.Request.json`. Use the ``location`` argument to :meth:`~reqparse.RequestParser.add_argument` to specify alternate locations to pull the values from. Any variable on the :class:`flask.Request` can be used. For example: :: # Look only in the POST body parser.add_argument('name', type=int, location='form') # Look only in the querystring parser.add_argument('PageSize', type=int, location='args') # From the request headers parser.add_argument('User-Agent', location='headers') # From http cookies parser.add_argument('session_id', location='cookies') # From file uploads parser.add_argument('picture', type=werkzeug.datastructures.FileStorage, location='files') .. note :: Only use ``type=list`` when ``location='json'``. `See this issue for more details `_ Multiple Locations ------------------ Multiple argument locations can be specified by passing a list to ``location``:: parser.add_argument('text', location=['headers', 'values']) When multiple locations are specified, the arguments from all locations specified are combined into a single :class:`~werkzeug.datastructures.MultiDict`. The last ``location`` listed takes precedence in the result set. If the argument location list includes the :attr:`~flask.Request.headers` location the argument names will no longer be case insensitive and must match their title case names (see :meth:`str.title`). Specifying ``location='headers'`` (not as a list) will retain case insensitivity. Parser Inheritance ------------------ Often you will make a different parser for each resource you write. The problem with this is if parsers have arguments in common. Instead of rewriting arguments you can write a parent parser containing all the shared arguments and then extend the parser with :meth:`~reqparse.RequestParser.copy`. You can also overwrite any argument in the parent with :meth:`~reqparse.RequestParser.replace_argument`, or remove it completely with :meth:`~reqparse.RequestParser.remove_argument`. For example: :: from flask_restful import reqparse parser = reqparse.RequestParser() parser.add_argument('foo', type=int) parser_copy = parser.copy() parser_copy.add_argument('bar', type=int) # parser_copy has both 'foo' and 'bar' parser_copy.replace_argument('foo', required=True, location='json') # 'foo' is now a required str located in json, not an int as defined # by original parser parser_copy.remove_argument('foo') # parser_copy no longer has 'foo' argument Error Handling -------------- The default way errors are handled by the RequestParser is to abort on the first error that occurred. This can be beneficial when you have arguments that might take some time to process. However, often it is nice to have the errors bundled together and sent back to the client all at once. This behavior can be specified either at the Flask application level or on the specific RequestParser instance. To invoke a RequestParser with the bundling errors option, pass in the argument ``bundle_errors``. For example :: from flask_restful import reqparse parser = reqparse.RequestParser(bundle_errors=True) parser.add_argument('foo', type=int, required=True) parser.add_argument('bar', type=int, required=True) # If a request comes in not containing both 'foo' and 'bar', the error that # will come back will look something like this. { "message": { "foo": "foo error message", "bar": "bar error message" } } # The default behavior would only return the first error parser = RequestParser() parser.add_argument('foo', type=int, required=True) parser.add_argument('bar', type=int, required=True) { "message": { "foo": "foo error message" } } The application configuration key is "BUNDLE_ERRORS". For example :: from flask import Flask app = Flask(__name__) app.config['BUNDLE_ERRORS'] = True .. warning :: ``BUNDLE_ERRORS`` is a global setting that overrides the ``bundle_errors`` option in individual :class:`~reqparse.RequestParser` instances. .. _error-messages: Error Messages -------------- Error messages for each field may be customized using the ``help`` parameter to ``Argument`` (and also ``RequestParser.add_argument``). If no help parameter is provided, the error message for the field will be the string representation of the type error itself. If ``help`` is provided, then the error message will be the value of ``help``. ``help`` may include an interpolation token, ``{error_msg}``, that will be replaced with the string representation of the type error. This allows the message to be customized while preserving the original error :: from flask_restful import reqparse parser = reqparse.RequestParser() parser.add_argument( 'foo', choices=('one', 'two'), help='Bad choice: {error_msg}' ) # If a request comes in with a value of "three" for `foo`: { "message": { "foo": "Bad choice: three is not a valid choice", } }