Jinja2 template variable if None Object set a default value

Question

How to make a variable in jijna2 default to \"\" if object is None instead of doing something like this?

      {% if p %}   
        {{ p.User[\'first_name\'         


        

Answer 1

I usually define an nvl function, and put it in globals and filters.

def nvl(*args):
    for item in args:
        if item is not None:
            return item
    return None

app.jinja_env.globals['nvl'] = nvl
app.jinja_env.filters['nvl'] = nvl

Usage in a template:

<span>Welcome {{ nvl(person.nick, person.name, 'Anonymous') }}<span>

// or 

<span>Welcome {{ person.nick | nvl(person.name, 'Anonymous') }}<span>

Answer 2

As addition to other answers, one can write something else if variable is None like this:

{{ variable or '' }}

Answer 3

{{p.User['first_name'] or 'My default string'}}