Conditionally join a list of strings in Jinja

Question

I have a list like

users = ['tom', 'dick', 'harry']

In a Jinja template I'd like to print a list of all users except tom joined. I cannot modify the variable before it's passed to the template.

I tried a list comprehension, and using Jinja's reject filter but I haven't been able to get these to work, e.g.

{{ [name for name in users if name != 'tom'] | join(', ') }}

gives a syntax error.

How can I join list items conditionally?

Answer 1

Use reject filter with sameas test:

>>> import jinja2
>>> template = jinja2.Template("{{ users|reject('sameas', 'tom')|join(',') }}")
>>> template.render(users=['tom', 'dick', 'harry'])
u'dick,harry'

UPDATE

If you're using Jinja 2.8+, use equalto instead of sameas as @Dougal commented; sameas tests with Python is, while equalto tests with ==.

Answer 2

This should work, as list comprehension is not directly supported. Ofcourse, appropiate filters will be better.

{% for name in users if name != 'tom'%}
    {{name}}
    {% if not loop.last %}
         {{','}}
    {% endif %}
{% endfor %}

Answer 3

Another solution with "equalto" test instead of "sameas"

Use reject filter with equalto test:

>>> import jinja2
>>> template = jinja2.Template("{{ items|reject('equalto', 'aa')|join(',') }}")
>>> template.render(users=['aa', 'bb', 'cc'])
u'bb,cc'