# Request Parsing¶

Warning

The whole request parser part of Flask-RESTPlus 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.

Flask-RESTPlus’s request parsing interface, reqparse, is modeled after the argparse interface. It’s designed to provide simple and uniform access to any variable on the flask.request object in Flask.

## Basic Arguments¶

Here’s a simple example of the request parser. It looks for two arguments in the flask.Request.values dict: an integer and a string

from flask_restplus import reqparse

parser = reqparse.RequestParser()
parser.add_argument('rate', type=int, help='Rate cannot be converted')
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 Error Messages for more details.

Note

By default, arguments are not required. Also, arguments supplied in the request that are not part of the RequestParser will be ignored.

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 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']


If you expect a coma separated list, use the action='split':

parser.add_argument('fruits', action='split')


This will let you make queries like

curl http://api.example.com -d "fruits=apple,lemon,cherry"


And your args will look like this :

args = parser.parse_args()
args['fruits']    # ['apple', 'lemon', 'cherry']


## 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 RequestParser tries to parse values from flask.Request.values, and flask.Request.json.

Use the location argument to add_argument() to specify alternate locations to pull the values from. Any variable on the flask.Request can be used. For example:

# Look only in the POST body

# Look only in the querystring



Note

Only use type=list when location='json'. See this issue for more details

Note

Using location='form' is way to both validate form data and document your form fields.

## 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 MultiDict. The last location listed takes precedence in the result set.

If the argument location list includes the headers location the argument names will no longer be case insensitive and must match their title case names (see str.title()). Specifying location='headers' (not as a list) will retain case insensitivity.

Sometimes, you need more than a primitive type to handle input validation. The inputs module provides some common type handling like:

You just have to use them as type argument:

parser.add_argument('flag', type=inputs.boolean)


See the inputs documentation for full list of available inputs.

You can also write your own:

def my_type(value):
'''Parse my type'''
if not condition:
raise ValueError('This is not my type')
return parse(value)

# Swagger documntation
my_type.__schema__ = {'type': 'string', 'format': 'my-custom-format'}


## 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 copy(). You can also overwrite any argument in the parent with replace_argument(), or remove it completely with remove_argument(). For example:

from flask_restplus import reqparse

parser = reqparse.RequestParser()

parser_copy = parser.copy()

# 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


To handle file upload with the RequestParser, you need to use the files location and to set the type to FileStorage.

from werkzeug.datastructures import FileStorage

type=FileStorage, required=True)

def post(self):
uploaded_file = args['file']  # This is FileStorage instance
return {'url': url}, 201


## 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_restplus import reqparse

parser = reqparse.RequestParser(bundle_errors=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()

{
"message":  {
"foo": "foo error message"
}
}


The application configuration key is “BUNDLE_ERRORS”. For example

from flask import Flask

app.config['BUNDLE_ERRORS'] = True


Warning

BUNDLE_ERRORS is a global setting that overrides the bundle_errors option in individual RequestParser instances.

## 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_restplus import reqparse

parser = reqparse.RequestParser()
# If a request comes in with a value of "three" for foo: