Adding css class to field on validation error in django

Expanding upon errx's answer.

Add the CSS

.error input, .error select {
    border: 2px red solid;
}

to specifically highlight the field

What about defining error_css_class? http://docs.djangoproject.com/en/dev/ref/forms/api/#styling-required-or-erroneous-form-rows?

class MyForm(ModelForm):
    error_css_class = 'error'

To answer the original question.

You can add the desired class to the field in the view to where you are submitting your form and doing your form.is_valid() check. Not the prettiest but it will work.

def submit_form(request):
    if request.method = 'POST':
        if. form.is_valid():
            # Do something with clean form data
            pass
        else:
            # Append css class to every field that contains errors.
            for field in form.errors:
                form[field].field.widget.attrs['class'] += ' my-css-class'
    return render(request, submit_form.html, {
        'form': form
    })