Flask receiving empty forms

Question

I'm trying to get a simple form set up in Flask for my own education. I've got a login.html page with this form code:

<form action="{{ url_for('login') }}" method="post">
    <div>
        <label for="username">Username</label>
        <div>
            <input type="text" id="username" name="username" placeholder="Username">
        </div>
    </div>
    <div>
        <label for="password">Password</label>
        <div>
            <input type="password" id="password" name="password" placeholder="Password">
        </div>
    </div>
    <div >
        <input class="btn" type="submit">
    </div>
</form>

I'm using code like the following to receive it, but Flask returns an empty request.form so I can't process it.

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        request.form['username']
        ...

I really don't want to learn another library (WTForms) right now, and I'm using bootstrap so that will add to the headache. What am I not seeing here with Flask/HTML?

does the request reaches your view function? Maybe form has different URL in action not "/login"? Try to put just "." in action. Just interested if it really lands in the view as you expect. — Ignas Butėnas, Dec 28 '12 at 09:44

score 38 · Answer 1 · answered May 26 '16 at 09:24

38

I had this problem, but it was because I forgot to assign a name attribute to my input elements and I was trying to refer access the form data by the id attribute instead

i.e.

My HTML and Python was as shown below

HTML

<input type="text" id="usernameTxtBx">

Python

request.form['usernameTxtBx']

What I have done now:

HTML

<input type="text" name="username" id="usernameTxtBx">

Python

request.form['username']

I also needed to ensure that I was using a POST request. A GET request gave me an empty dictionary in my python code.

The OP made neither of these mistakes. But this may help someone that stumbles on this thread.

answered May 26 '16 at 09:24

Resonance

3,359
2
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4

`id="usernameTxtBx"` is unnecessary, as it's not reflected in the request. You can access GET and POST variables together though `request.args` instead of `request.form` which only accesses POST – avloss Feb 16 '17 at 06:14
Thank you! WTForms seems great, but is simply overkill for my needs. – Dave C Oct 27 '20 at 15:07

score 14 · Answer 2 · edited May 23 '17 at 12:33

I had that problem. Some tools like postman or some libraries or web browser sends the data in a way that flask does not identify as posted values. From my point of view this is a flask issue.

This is the workaround I followed to solve it: 1 - I sent the information using json. Have a look to this:

How to send a JSON object using html form data

2 - I instead of getting the parameters using: value = request.form["myparamname"] I used this:

json_data = request.get_json(force=True) 

value = json_data["myparamname"]

score 0 · Answer 3 · answered Sep 29 '22 at 16:54

0

just use request.get_json() in POST requests

answered Sep 29 '22 at 16:54

DanteDX

1,059
7
12

score -3 · Answer 4 · answered Dec 03 '13 at 14:12

login.html

{% extends "layout.html" %}

{% block content %}
  <div class="form">
    <h2>Sign In</h2>

 {% for field in form.errors %}
{% for error in form.errors[field] %}
    <div class="alert alert-error">
        <strong>Oops...</strong> {{error}}.
    </div>
{% endfor %}
{% endfor %}

  <form action="{{ url_for('login') }}" method=post>
    {{ form.hidden_tag() }}

    {{ form.email.label }}
    {{ form.email }}

    {{ form.password.label }}
    {{ form.password }}

      <p> <input id="submit" name="submit" type="submit" class="btn btn-inverse" value="Sign In"></p>
  </form>
</div>
{% endblock %}

forms.py

  class SigninForm(Form):
        email = TextField("email", [validators.Required("Please enter your email")])
        password = PasswordField('Password', [validators.Required("Please enter a password.")])
        submit = SubmitField("Sign In")

Then import the signinform in your views and create your login method like this

@app.route('/login', methods=['GET', 'POST'])
def signin():
  form = SigninForm()
  if form.validate_on_submit():
      session['email'] = form.email.data

      flash('You are logged in')
      return redirect(url_for('dashboard'))
  return render_template('signin.html', form=form)

Refer this tutorial for more detailed instructions http://pypix.com/python/building-flask-blog-part-1/

Flask receiving empty forms

4 Answers4