Wtforms, add a class to a form dynamically

Question

is there a way i could send a form's (css) class from python? For example:

class Company(Form):
    companyName = TextField('Company Name', [validators.Length(min=3, max = 60)])

This renders a simple text field, but i want that text field to have the css class of .companyName, is that possible directly from python?

I know that i can put a id="companyName" directly from python, but not class.

Help.

Update: I tried class_="companyName" and it did not work, i got:

__init__() got an unexpected keyword argument '_class'

Solution 1

WTForms does not allow you to set display options (such as class name) in the field initialization. However, there are several ways to get around this:

1. If all of your fields should include a class name as well as an ID then just pass in each field's short_name to it when you render it:

   <dl>
   {% for field in form %}
   <dt>{{field.label}}</dt>
   <dd>{{field(class_=field.short_name)}}</dd>
   {% endfor %}
   </dl>
   

2. Create a custom widget mixin that provides the class name:

   from wtforms.fields import StringField
   from wtforms.widgets import TextInput
   
   class ClassedWidgetMixin(object):
       """Adds the field's name as a class 
       when subclassed with any WTForms Field type.
   
       Has not been tested - may not work."""
       def __init__(self, *args, **kwargs):
           super(ClassedWidgetMixin, self).__init__(*args, **kwargs)
   
       def __call__(self, field, **kwargs):
           c = kwargs.pop('class', '') or kwargs.pop('class_', '')
           kwargs['class'] = u'%s %s' % (field.short_name, c)
           return super(ClassedWidgetMixin, self).__call__(field, **kwargs)
   
   # An example
   class ClassedTextInput(ClassedWidgetMixin, TextInput):
       pass
   
   class Company(Form):
       company_name = StringField('Company Name', widget=ClassedTextInput)
   

Solution 2

Alternatively you can add the class in your template like this for jinja2:

{{ form.name(size=20, class_='input-small') }}

Solution 3

Use render_kw if using WTForms >= 2.1 :

submit = SubmitField(u'Block Submit Buttom', render_kw={"class": "btn btn-primary btn-block"})

Comments

[sofly]

Saved me as well :) This is a wonderful solution, not sure why an example along these lines isn't somewhere in the WTForm docs

[benjaminz]

I'd vote up ten times if it is possible, this is a much better solution. Now I can sit back and watch WTForms rock~~~

[benjaminz]

Although the underscore after class doesn't seem to be necessary

[David]

In Python functions you can't use "class" as a named argument because it's a language keyword. For example, myfunc(class='xyz') results in a SyntaxError. Using the myfunc(**{'class': 'xyz'}) like shown above gets around that problem. Thanks for your example!

[renatov]

This solution is much better than the one chosen as the correct answer.

[Tony Chou]

It works for me many days age, but it just failed now. I don't remember what I did then, but almost just like your answer. After Ctrl+F5, the submit button also shows it class btn btn-default:-(... Any possible errors? WTForms==2.1 and Flask-WTF==0.14.2

[Sukma Saputra]

It's perfectly what I need when I use parsley js for email validate.