问python每3次迭代添加一个新的div

EN

{% for product in category.products.all %}
        <div class="{% cycle 'clear' '' '' %}">
            <a href="{% url shop.views.product category.slug product.slug %}"><img src="{{MEDIA_URL}}{{product.mini_thumbnail}}" alt="{{product.name}}" class="thumbnail"/></a>
            <div class="prod-details">
            <h3><a href="{% url shop.views.product category.slug product.slug %}">{{product.get_product_name}}</a></h3>
            <h4 class="strap">{{product.get_product_detail}}</h4>
            <p>{{ product.strap }}</p>
            <ul>
                <li class="price">&pound;{{product.price}}</li>
                <li class="quantity">
                    <select name="quantity_{{product.id}}">
                        <option label="1" value="1">1</option>
                        <option label="2" value="2">2</option>
                        <option label="3" value="3">3</option>
                        <option label="4" value="4">4</option>
                        <option label="5" value="5">5</option>
                        <option label="6" value="6">6</option>
                        <option label="7" value="7">7</option>
                        <option label="8" value="8">8</option>
                        <option label="9" value="9">9</option>
                    </select>
                </li>
                <li><a href="{% url shop.views.product category.slug product.slug %}">Details &gt;</a></li>
                <li class="right"><input type="submit" name="add_to_basket_{{product.id}}" value="Add to Basket &gt;"/></li>
            </ul>
            </div>
        </div>
    {% endfor %}