Flask Snippets

Render WTForm fields with html attributes that cause TemplateSyntaxErrors

By Josh Klein filed in Forms

Suppose you had a WTForm TextField that you wanted to use a javascript library like bootstrap-typeahead.js on. You might want the field to render as:

<input type="text" data-provide='typeahead', data-items='3', data-source='["x","y","z"]'>

After creating a WTForm in the view and passing it to your template, your first attempt would be to pass the additional keyword arguments:

{{ form.myfield(name='test', data-provide='typeahead', data-data-items='3', data-source='["x","y","z"]') }}

But this will lead to a TemplateSyntaxError because a dash is the subtraction operator in Python, and we can't escape the character in a keyword argument's key.

Instead, pass the HTML attributes that contain invalid syntax as an ad-hoc dictionary:

{{ form.myfield(name='test', **{'data-provide':'typeahead','data-items':'3','data-source': '["x","y","z"]'}) }}

This snippet by Josh Klein can be used freely for anything you like. Consider it public domain.