sim3x

t = l.add_xpath('ibp_power_w', "//div[@class='characteristic' and text()[contains(normalize-space(.), '%s')]]/following-sibling::div[@class = 'value']/text()" % u"Мощность (Вт)" )

print t.strip()

In [8]: set(l2) - set(l1)
Out[8]: {2, 4}

In [9]: [x for x in l2 if x not in l1]
Out[9]: [2, 4]

{% if post.image %}
    <p><img src="{{post.image.url}}"></p>
{% else %}
   <p></p>
{% endif %}