WTForms getting the errors

Question

Currently in WTForms to access errors you have to loop through field errors like so:

for error in form.username.errors:
        print error

Since I'm building a rest application which uses no form views, I'm forced to check through all form fields in order to find where the error lies.

Is there a way I could do something like:

for fieldName, errorMessage in form.errors:
        ...do something

Gesualdo

Answer 1

The actual form object has an errors attribute that contains the field names and their errors in a dictionary. So you could do:

for fieldName, errorMessages in form.errors.items():
    for err in errorMessages:
        # do something with your errorMessages for fieldName

Fere

Answer 2

A cleaner solution for Flask templates:

Python 3:

{% for field, errors in form.errors.items() %}
<div class="alert alert-error">
    {{ form[field].label }}: {{ ', '.join(errors) }}
</div>
{% endfor %}

Python 2:

{% for field, errors in form.errors.iteritems() %}
<div class="alert alert-error">
    {{ form[field].label }}: {{ ', '.join(errors) }}
</div>
{% endfor %}

Wholehearted

This is the best effort on this page. But it looks like somebody took a crap on my form. Exposes the form names too, for my end-users to figure out what cli_tel actually is... Though I might be the only one that cares? – Jessejessee

@PeterLada: that's the stupid thing... the errors variable doesn't really provide that. You can do it with something like this I think: form[field].name – Wholehearted

If you use python3, use items() instead of iteritems() – Uta

instead of using just label. Use label.text. ie: flash(''.join([f'{form[f].label.text}: {"".join(e)} ' for f, e in form.errors.items()])). Removes the html. – Patent

Answer 3

For anyone looking to do this in Flask templates:

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

Heretofore

Answer 4

With ModelFormFields in SqlAlchemy when used with WTForms, if you have a nested object inside an object (foreign key relationships), here is how you show the relevant errors for fields properly.

Python side:

def flash_errors(form):
    for field, errors in form.errors.items():
        if type(form[field]) == ModelFormField:
            for error, lines in errors.iteritems():
                description = "\n".join(lines)
                flash(u"Error in the %s field - %s" % (
                    #getattr(form, field).label.text + " " + error,
                    form[field][error].label.text,
                    description
                ))
        else:
            for error, lines in errors.iteritems():
                description = "\n".join(lines)
                flash(u"Error in the %s field - %s" % (
                    #getattr(form, field).label.text + " " + error,
                    form[field].label.text,
                    description
                ))

Jinja side:

  {% with messages = get_flashed_messages(with_categories=true) %}
    {% for message in messages %}
      {% if "Error" not in message[1]: %}
        <div class="alert alert-info">
          <strong>Success! </strong> {{ message[1] }}
        </div>
      {% endif %}

      {% if "Error" in message[1]: %}
        <div class="alert alert-warning">
         {{ message[1] }}
        </div>
      {% endif %}
    {% endfor %}
  {% endwith %}

Hope that helps.

Barrybarrymore