Get the data received in a Flask request
PythonFlaskWerkzeugPython Problem Overview
I want to be able to get the data sent to my Flask app. I've tried accessing request.data
but it is an empty string. How do you access request data?
from flask import request
@app.route('/', methods=['GET', 'POST'])
def parse_request():
data = request.data # data is empty
# need posted data here
The answer to this question led me to ask https://stackoverflow.com/q/10999990 next, which is about getting the raw data rather than the parsed data.
Python Solutions
Solution 1 - Python
The docs describe the attributes available on the request
object (from flask import request
) during a request. In most common cases request.data
will be empty because it's used as a fallback:
> request.data
Contains the incoming request data as string in case it came with a mimetype Flask does not handle.
request.args
: the key/value pairs in the URL query stringrequest.form
: the key/value pairs in the body, from a HTML post form, or JavaScript request that isn't JSON encodedrequest.files
: the files in the body, which Flask keeps separate fromform
. HTML forms must useenctype=multipart/form-data
or files will not be uploaded.request.values
: combinedargs
andform
, preferringargs
if keys overlaprequest.json
: parsed JSON data. The request must have theapplication/json
content type, or userequest.get_json(force=True)
to ignore the content type.
All of these are MultiDict
instances (except for json
). You can access values using:
-
request.form['name']
: use indexing if you know the key exists -
request.form.get('name')
: useget
if the key might not exist -
request.form.getlist('name')
: usegetlist
if the key is sent multiple times and you want a list of values.get
only returns the first value.
Solution 2 - Python
To get the raw data, use request.data
. This only works if it couldn't be parsed as form data, otherwise it will be empty and request.form
will have the parsed data.
from flask import request
request.data
Solution 3 - Python
For URL query parameters, use request.args
.
search = request.args.get("search")
page = request.args.get("page")
For posted form input, use request.form
.
email = request.form.get('email')
password = request.form.get('password')
For JSON posted with content type application/json
, use request.get_json()
.
data = request.get_json()
Solution 4 - Python
Here's an example of parsing posted JSON data and echoing it back.
from flask import Flask, request, jsonify
app = Flask(__name__)
@app.route('/foo', methods=['POST'])
def foo():
data = request.json
return jsonify(data)
To post JSON with curl:
curl -i -H "Content-Type: application/json" -X POST -d '{"userId":"1", "username": "fizz bizz"}' http://localhost:5000/foo
Or to use Postman:
Solution 5 - Python
To get the raw post body regardless of the content type, use request.get_data()
. If you use request.data
, it calls request.get_data(parse_form_data=True)
, which will populate the request.form
MultiDict
and leave data
empty.
Solution 6 - Python
If you post JSON with content type application/json
, use request.get_json()
to get it in Flask. If the content type is not correct, None
is returned. If the data is not JSON, an error is raised.
@app.route("/something", methods=["POST"])
def do_something():
data = request.get_json()
Solution 7 - Python
To get request.form
as a normal dictionary , use request.form.to_dict(flat=False)
.
To return JSON data for an API, pass it to jsonify
.
This example returns form data as JSON data.
@app.route('/form_to_json', methods=['POST'])
def form_to_json():
data = request.form.to_dict(flat=False)
return jsonify(data)
Here's an example of POST form data with curl, returning as JSON:
$ curl http://127.0.0.1:5000/data -d "name=ivanleoncz&role=Software Developer"
{
"name": "ivanleoncz",
"role": "Software Developer"
}
Solution 8 - Python
Use request.get_json()
to get posted JSON data.
data = request.get_json()
name = data.get('name', '')
Use request.form
to get data when submitting a form with the POST method.
name = request.form.get('name', '')
Use request.args
to get data passed in the query string of the URL, like when submitting a form with the GET method.
request.args.get("name", "")
request.form
etc. are dict-like, use the get
method to get a value with a default if it wasn't passed.
Solution 9 - Python
To get JSON posted without the application/json
content type, use request.get_json(force=True)
.
@app.route('/process_data', methods=['POST'])
def process_data():
req_data = request.get_json(force=True)
language = req_data['language']
return 'The language value is: {}'.format(language)
Solution 10 - Python
To post JSON with jQuery in JavaScript, use JSON.stringify
to dump the data, and set the content type to application/json
.
var value_data = [1, 2, 3, 4];
$.ajax({
type: 'POST',
url: '/process',
data: JSON.stringify(value_data),
contentType: 'application/json',
success: function (response_data) {
alert("success");
}
});
Parse it in Flask with request.get_json()
.
data = request.get_json()
Solution 11 - Python
Import request:
from flask import request
URL query parameters:
name = request.args.get("name")
age = request.args.get("age")
Form Input:
name = request.form.get('name')
age = request.form.get('age')
OR (use indexing if you know the key exists, specify the name of input fields)
name = request.form['name']
age = request.form['age']
JSON Data (for content type application/json)
data = request.get_json()
Solution 12 - Python
The raw data is passed in to the Flask application from the WSGI server as request.stream
. The length of the stream is in the Content-Length
header.
length = request.headers["Content-Length"]
data = request.stream.read(length)
It is usually safer to use request.get_data()
instead.
Solution 13 - Python
Here's an example of posting form data to add a user to a database. Check request.method == "POST"
to check if the form was submitted. Use keys from request.form
to get the form data. Render an HTML template with a <form>
otherwise. The fields in the form should have name
attributes that match the keys in request.form
.
from flask import Flask, request, render_template
app = Flask(__name__)
@app.route("/user/add", methods=["GET", "POST"])
def add_user():
if request.method == "POST":
user = User(
username=request.form["username"],
email=request.form["email"],
)
db.session.add(user)
db.session.commit()
return redirect(url_for("index"))
return render_template("add_user.html")
<form method="post">
<label for="username">Username</label>
<input type="text" name="username" id="username">
<label for="email">Email</label>
<input type="email" name="email" id="email">
<input type="submit">
</form>
Solution 14 - Python
To parse JSON, use request.get_json()
.
@app.route("/something", methods=["POST"])
def do_something():
result = handle(request.get_json())
return jsonify(data=result)
Solution 15 - Python
When writing a Slack bot, which is supposed to send JSON data, I got a payload where the Content-Type
was application/x-www-form-urlencoded
.
I tried request.get_json()
and it didn't work.
@app.route('/process_data', methods=['POST'])
def process_data():
req_data = request.get_json(force=True)
Instead I used request.form
to get the form data field that contained JSON, then loaded that.
from flask import json
@ app.route('/slack/request_handler', methods=['POST'])
def request_handler():
req_data = json.loads(request.form["payload"])
Solution 16 - Python
If the content type is recognized as form data, request.data
will parse that into request.form
and return an empty string.
To get the raw data regardless of content type, call request.get_data()
. request.data
calls get_data(parse_form_data=True)
, while the default is False
if you call it directly.
Solution 17 - Python
If the body is recognized as form data, it will be in request.form
. If it's JSON, it will be in request.get_json()
. Otherwise the raw data will be in request.data
. If you're not sure how data will be submitted, you can use an or
chain to get the first one with data.
def get_request_data():
return (
request.args
or request.form
or request.get_json(force=True, silent=True)
or request.data
)
request.args
contains args parsed from the query string, regardless of what was in the body, so you would remove that from get_request_data()
if both it and a body should data at the same time.
Solution 18 - Python
You can get request data from
request.form
for form data, this includes form and file data,request.json
andrequest.get_json
for JSON datarequest.headers
for headersrequest.args
to get query params
They're all like a dictionary, use request.form['name']
if you know the key exists, or request.form.get('name')
if it is optional.
Solution 19 - Python
When posting form data with an HTML form, be sure the input
tags have name
attributes, otherwise they won't be present in request.form
.
@app.route('/', methods=['GET', 'POST'])
def index():
print(request.form)
return """
<form method="post">
<input type="text">
<input type="text" id="txt2">
<input type="text" name="txt3" id="txt3">
<input type="submit">
</form>
"""
ImmutableMultiDict([('txt3', 'text 3')])
Only the txt3
input had a name
, so it's the only key present in request.form
.
Solution 20 - Python
@app.route('/addData', methods=['POST'])
def add_data():
data_in = mongo.db.Data
id = request.values.get("id")
name = request.values.get("name")
newuser = {'id' : id, 'name' : name}
if voter.find({'id' : id, 'name' : name}).count() > 0:
return "Data Exists"
else:
data_in.insert(newuser)
return "Data Added"
Solution 21 - Python
I just faced the same need. I have to save information in case of any unexpected situation. So, I use the following formula:
Info = "%s/%s/%s" % (request.remote_addr, repr(request), repr(session))
repr(request) will give a string representation of the basic information. You could add user-agent data with: request.headers.get('User-Agent')
I also save the session continent as it could contain valuable information
Solution 22 - Python
Try - >
from flask import request
@app.route('/', methods=['GET', 'POST'])
def parse_request():
if request.method == 'POST':
data = request.form.get('data')
Solution 23 - Python
request.data
This is great to use but remember that it comes in as a string and will need iterated through.