How to get form data in Flask?

Question

I need get data from form.

I use JavaScript to create form:

<script>   
function checkAuth() {
                var user = ADAL.getCachedUser();
                if (user) {
                    var form = $('<form style="position: absolute; width: 0; height: 0; opacity: 0; display: none; visibility: hidden;" method="POST" action= "{{ url_for("general.microsoft") }}">');

                    form.append('<input type="hidden" name="token" value="' + ADAL.getCachedToken(ADAL.config.clientId) + '">');
                    form.append('<input type="hidden" name="json" value="' + encodeURIComponent(JSON.stringify(user)) + '">');
                    $("body").append(form);
                    form.submit();
                }
            }
</script> 

then I need to get data from the input field which name="json".

Here is my view function:

@general.route("/microsoft/", methods=["GET", "POST"])
@csrf.exempt
def microsoft():
    form = cgi.FieldStorage()
    name = form['json'].value
    return name

But I get an error:

builtins.KeyError KeyError: 'json'

Help me get data from form.

Answer 1

You can get form data from Flask's request object with the form attribute:

from flask import Flask, request
app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    data = request.form['input_name']  # pass the form field name as key
    ...
    

You can also set a default value to avoid 400 errors with the get() method since the request.form attribute is a dict-like object:

from flask import Flask, request
app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    default_value = '0'
    data = request.form.get('input_name', default_value)
    ...