[Django]-Django Forms: if not valid, show form with error message

by

302👍

✅

If you render the same view when the form is not valid then in template you can access the form errors using form.errors.

{% if form.errors %}
    {% for field in form %}
        {% for error in field.errors %}
            <div class="alert alert-danger">
                <strong>{{ error|escape }}</strong>
            </div>
        {% endfor %}
    {% endfor %}
    {% for error in form.non_field_errors %}
        <div class="alert alert-danger">
            <strong>{{ error|escape }}</strong>
        </div>
    {% endfor %}
{% endif %}

An example:

def myView(request):
    form = myForm(request.POST or None, request.FILES or None)
    if request.method == 'POST':
        if form.is_valid():
            return HttpResponseRedirect('/thanks/')
    return render(request, 'my_template.html', {'form': form})
👤Aamir Rind

22👍

views.py

from django.contrib import messages 

def view_name(request):
    if request.method == 'POST':
        form = form_class(request.POST)
        if form.is_valid():
            return HttpResponseRedirect('/thanks'/)
        else:
            messages.error(request, "Error")
return render(request, 'page.html', {'form':form_class()})

If you want to show the errors of the form other than that not valid just put {{form.as_p}} like what I did below

page.html

<html>
    <head>
        <script>
            {% if messages %}
                {% for message in messages %}
                    alert('{{message}}')
                {% endfor %}
            {% endif %}
        </script>
    </head>
    <body>
        {{form.as_p}}
    </body>
</html>
👤catherine

5👍

UPDATE:
Added a more detailed description of the formset errors.

Form.errors combines all field and non_field_errors. Therefore you can simplify the html to this:

template

    {% load form_tags %}

    {% if form.errors %}
    <div class="alert alert-danger alert-dismissible col-12 mx-1" role="alert">
        <div id="form_errors">
            {% for key, value in form.errors.items %}
                <span class="fieldWrapper">
                    {{ key }}:{{ value }}
                </span>
            {% endfor %}
        </div>
        <button type="button" class="close" data-dismiss="alert" aria-label="Close">
            <span aria-hidden="true">&times;</span>
        </button>
    </div>
    {% endif %}


If you want to generalise it you can create a list_errors.html which you include in every form template. It handles form and formset errors:

    {% if form.errors %}
    <div class="alert alert-danger alert-dismissible col-12 mx-1" role="alert">
        <div id="form_errors">

            {% for key, value in form.errors.items %}
                <span class="fieldWrapper">
                    {{ key }}:{{ value }}
                </span>
            {% endfor %}
        </div>
        <button type="button" class="close" data-dismiss="alert" aria-label="Close">
            <span aria-hidden="true">&times;</span>
        </button>
    </div>
    {% elif formset.total_error_count %}
    <div class="alert alert-danger alert-dismissible col-12 mx-1" role="alert">
        <div id="form_errors">
            {% if formset.non_form_errors %}
                {{ formset.non_form_errors }}
            {% endif %}
            {% for form in formset.forms %}
                {% if form.errors %}
                    Form number {{ forloop.counter }}:
                    <ul class="errorlist">
                    {% for key, error in form.errors.items %}
                        <li>{{form.fields|get_label:key}}
                            <ul class="errorlist">
                                <li>{{error}}</li>
                            </ul>
                        </li>
                    {% endfor %}
                    </ul>
                {% endif %}
            {% endfor %}

        </div>
    </div>

    {% endif %}

form_tags.py

from django import template

register = template.Library()


def get_label(a_dict, key):
    return getattr(a_dict.get(key), 'label', 'No label')


register.filter("get_label", get_label)

One caveat: In contrast to forms Formset.errors does not include non_field_errors.

👤P. Maino

4👍

def some_view(request):
    if request.method == 'POST':
        form = SomeForm(request.POST)
        if form.is_valid():
            return HttpResponseRedirect('/thanks'/)
    else:
        form = SomeForm()
    return render(request, 'some_form.html', {'form': form})
👤Lukasz Koziara

4👍

This answer is correct but has a problem: fields not defined.
If you have more then one field, you can not recognize which one has error.

with this change you can display field name:

{% if form.errors %}
    {% for field in form %}
        {% for error in field.errors %}
            <div class="alert alert-danger">
                <strong>{{ field.label }}</strong><span>{{ error|escape }}</strong>
            </div>
        {% endfor %}
    {% endfor %}
    {% for error in form.non_field_errors %}
        <div class="alert alert-danger">
            <strong>{{ error|escape }}</strong>
        </div>
    {% endfor %}
{% endif %}
👤Chalist

2👍

@AamirAdnan’s answer missing field.label; the other way to show the errors in few lines.

{% if form.errors %}
    <!-- Error messaging -->
    <div id="errors">
        <div class="inner">
            <p>There were some errors in the information you entered. Please correct the following:</p>
            <ul>
                {% for field in form %}
                    {% if field.errors %}<li>{{ field.label }}: {{ field.errors|striptags }}</li>{% endif %}
                {% endfor %}
            </ul>
        </div>
    </div>
    <!-- /Error messaging -->
{% endif %}
👤Laxmikant Ratnaparkhi

0👍

simply you can do like this because when you initialized the form in contains form data and invalid data as well:

def some_func(request):
    form = MyForm(request.POST)
    if form.is_valid():
         //other stuff
    return render(request,template_name,{'form':form})

if will raise the error in the template if have any but the form data will still remain as :

error_demo_here

👤Dinesh Kc

-1👍

You can put simply a flag variable, in this case is_successed.

def preorder_view(request, pk, template_name='preorders/preorder_form.html'):
    is_successed=0
    formset = PreorderHasProductsForm(request.POST)
    client= get_object_or_404(Client, pk=pk)
    if request.method=='POST':
        #populate the form with data from the request
       # formset = PreorderHasProductsForm(request.POST)
        if formset.is_valid():
            is_successed=1
            preorder_date=formset.cleaned_data['preorder_date']
            product=formset.cleaned_data['preorder_has_products']
            return render(request, template_name, {'preorder_date':preorder_date,'product':product,'is_successed':is_successed,'formset':formset})



    return render(request, template_name, {'object':client,'formset':formset})

afterwards in your template you can just put the code below

{%if is_successed == 1 %}
<h1>{{preorder_date}}</h1>
<h2> {{product}}</h2>
{%endif %}
👤gtopal

Leave a comment