Why can I call the "all" method on my ManyRelatedManager without parenthesis? (Django)

Question

I'm following the tutorial in the Django documentation, and experimenting with models and views. I have a Person model, which has a many-to-many relationship to other Persons, which I call "friends". I wanted to show a list of people in my database, and their friends, so I tried the following template:

{% if people %}
    <ul>
    {% for p in people %}
        <li>
            {{ p.name }}
            <ul>
            {% for f in p.friends.all() %}
                <li>
                    {{ f.name }}
                </li>
            {% endfor %}
            </ul>
        </li>
    {% endfor %}
    </ul>
{% else %}
    <p>There are no people.</p>
{% endif %}

Django tells me that it cannot find the all() method. In a wild guess I try to take away the parentheses, leaving the line as follows {% for f in p.friends.all %}. To my surprise, this actually works, but I cannot understand why.

Am I actually calling the method and getting a query set back, or is something completely different going on?

Answer 1

As Victor Castillo Torres points out in a comment, in Django templates you do not include parentheses in method calls. Only methods without parameters can be called, and these are called without parentheses.

Further details in the Django documentation: https://docs.djangoproject.com/en/dev/topics/templates/#variables