How can I get the validation errors from flask_wtforms - flask

Question

I would like to get validation errors from a textarea form from flask_wtforms. I know that you can get them by including this in the html :
{% for error in form.post.errors %}
{{ error }}
{% endfor %}
But that doesn't quite work for me because Im using a bootstrap modal and the Length validation requires you to submit the form, refreshing the page, unlike the DataRequired() validator which prevents you from submitting. And its hard to tell that the form failed.
Basically I would like to get the errors from the python end and flash them.
I've tried to access the errors with form.post.errors but it doesn't work, it always returns an empty set.
This is the code for my index
def index():
form = PostForm()
// I would like to get the errors via form.post.errors here and I don't understand why I can't
if form.validate_on_submit():
post = Post(body=form.post.data, author=current_user)
db.session.add(post)
db.session.commit()
flash('Your post is now live!', 'primary')
return redirect(url_for('index'))
page = request.args.get('page', 1, type=int)
posts = current_user.followed_posts().paginate(page, app.config['POSTS_PER_PAGE'], False)
next_url = url_for('index', page=posts.next_num) if posts.has_next else None
prev_url = url_for('index', page=posts.prev_num) if posts.has_prev else None
return render_template('index.html', title='Home', posts=posts.items, form=form, next_url=next_url, prev_url=prev_url)
{% extends "base.html" %}
{% block content %}
{% if form %}
<div class="modal fade" id="submitPost" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
<div class="modal-dialog" role="document">
<form action="" method="post">
{{ form.hidden_tag() }}
<div class="modal-content">
<div class="modal-header">
<h5 class="modal-title" id="submitPostLabel">Submit Post</h5>
<button type="button" class="close" data-dismiss="modal" aria-label="Close">
<span aria-hidden="true">×</span>
</button>
</div>
<div class="modal-body">
<div class="form-group">
<label for="PostText">{{ form.post.label }}</label>
{{ form.post(cols=32, rows=4, class="form-control") }}<br>
</div>
</div>
<div class="modal-footer">
<!-- <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button> -->
{{ form.submit(class="btn btn-primary") }}
</div>
</div>
</form>
</div>
</div>
{% endif %}
the above html file is basically
<form action="" method="post">
{{ form.hidden_tag() }}
{{ form.post.label }}
{{ form.post(cols=32, rows=4, class="form-control") }}
{{ form.submit(class="btn btn-primary") }}
</form>
with some bootstrap

Answer 1

You can print the errors by adding the following: print form.errors.items().
form.errors