verrochio verrochio - 6 months ago 100
Python Question

Wtforms, add a class to a form dynamically

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'

Answer

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)
    
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