my_dict = {"First tab": "tab1", "Second tab": "tab2", "Third tab": "tab3"}

<ul class="nav nav-pills nav-fill" id="pills-tab" role="tablist">
    {% for name, attr in my_dict.items() %}

        {% if loop.index == 1 %}
            <li class="nav-item">
                <a class="nav-link active" id="{{ attr }}" data-toggle="pill" href="#{{ attr }}" role="tab"
                   aria-controls="{{ attr }}_c" aria-selected="true">{{ name }}
                </a>
            </li>

        {% else %}
            <li class="nav-item">
                <a class="nav-link" id="{{ attr }}" data-toggle="pill" href="#{{ attr }}" role="tab"
                   aria-controls="{{ attr }}_c" aria-selected="false">{{ name }}
                </a>
            </li>
        {% endif %}
    {% endfor %}
</ul>

<div class="tab-content" id="pills-tabContent">

    {% for attr in my_dict.values() %}

        {% if loop.index == 1 %}

            <div class="tab-pane fade show active" id="{{ attr }}_c" role="tabpanel"
                 aria-labelledby="{{ attr }}">
                <h4>This is a tab</h4>
            </div>

        {% else %}

            <div class="tab-pane fade" id="{{ attr }}_c" role="tabpanel" aria-labelledby="{{ attr }}">
                <h4>Hope this works</h4>
            </div>

        {% endif %}

    {% endfor %}

</div>