exemplo jinja2 tojson

template_jijja2.py

def template(html, **params):
    import jinja2

    env = jinja2.Environment(loader=FileSystemLoader(''))

    def tojson(s):                                       
        import json
        return json.dumps(s)

    env.filters['tojson'] = tojson
    template = env.from_string(html)
    return template.render(context=params, **params)

print(template('{{ context|tojson }}', name='slex', value=39 ))