函数没有在Python中调用，为什么？我该如何解决它？

我目前工作的Python/Django的网站，此刻我有一个模板，看起来像这样函数没有在Python中调用，为什么？我该如何解决它？

{% extends "shopbase.html" %} 
{% block pageid %}products{% endblock %} 
{% block right-content %} 

<img src="{{MEDIA_URL}}/local/images/assets/products.png" alt="Neal and Wolf News" class="position"/> 
    <div class="products"> 
    <form method="post" action="{% url category category.slug %}"> 
    {% for product in category.products.all %} 
     <div class="{% cycle 'clear' '' '' %}"> 
      <img src="{{MEDIA_URL}}{{download.mini.thumbnail}}" alt="{{product.name}}" class="thumbnail"/> 
      <h3><a href="{% url shop.views.product category.slug product.slug %}">{{ product.product_type_name }}</a></h3> 
      <p class="strap">{{ product.product_sub_name }}</p> 
      <p>{{ product.strap }}</p> 
      <ul class="clear"> 
       <li class="price"><b>&pound;{{product.price}}</b></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><b><a href="details">Details &gt;</a></b></li> 
       <li><input type="submit" name="add_to_basket_{{product.id}}" value="Add to Basket &gt;"/></a></li> 
      </ul> 
     </div> 
    {% endfor %} 
    </form> 
    </div> 
{% endblock %}

，并在模型中我有一个类，看起来像这样

def get_thumbnail(self, dimension, on=RES_X, use=USE_BOTH): 
    """ 
    Generate a thumbnail image for this Store Object. The thumbnail will be 
    of size 'dimension' on the axis specified by the on parameter (which is 
    deduced from calling x_or_y). If the use parameter is set to USE_BOTH 
    then the thumbnail will take priority in the generation order. In other 
    words, the function checks for the existance of an uploaded thumbnail. 
    If one exists, it will use that, otherwise the image field is used 
    instead. Specifying either USE_IMAGE or USE_THUMBNAIL here will force 
    the generation to a particular asset. 
    The image is saved out as a jpeg with the quality set to 90. The 
    path relative to the MEDIA_ROOT is then returned. 
    """ 
    from PIL import Image 
    import os 

    if self.thumbnail and use != StoreObject.USE_IMAGE: 
     source_path = str(self.thumbnail) 
    elif self.image and use != StoreObject.USE_THUMBNAIL: 
     source_path = str(self.image) 
    else: 
     return "" 

    try: 
     against = StoreObject.x_or_y(on) 
    except KeyError: 
     return "" 

    target_path = os.path.join(StoreObject.GENERATED_THUMB_LOCATION, "%s-%d%s.png" % (self.slug, dimension, against)) 

    savepath = os.path.join(settings.MEDIA_ROOT, target_path) 
    loadpath = os.path.join(settings.MEDIA_ROOT, source_path) 

    if os.path.exists(savepath) and os.path.getmtime(savepath) > os.path.getmtime(loadpath): 
     return target_path 

    try: 
     img = Image.open(loadpath) 
    except IOError: 
     return "" 

    aspect = float(img.size[0])/float(img.size[1]) 
    if against == StoreObject.RES_X: 
     height = dimension/aspect 
     width = dimension 
    elif against == StoreObject.RES_Y: 
     width = dimension * aspect 
     height = dimension 

    img = img.resize((width,height), Image.ANTIALIAS) 

    img.convert('RGBA').save(savepath, "PNG") 
    return target_path 

def mini_thumbnail(self): 
    """ 
    Generate and return the path to, a thumbnail that is 50px high 
    """ 
    return self.get_thumbnail(50, "x") 

def preview_image(self): 
    """ 
    Generate and return the path to, a thumbnail that is 300px wide, build 
    from the image field 
    """ 
    return self.get_thumbnail(300, use=StoreObject.USE_IMAGE) 

def preview_thumbnail(self): 
    """ 
    Generate and return the path to, a thumbnail that is 300px wide, build 
    from the thumbnail field 
    """ 
    return self.get_thumbnail(300, use=StoreObject.USE_THUMBNAIL)

现在正如你所看到的，我试图从数据库中提取某些项目的某些信息，并在缩略图中显示该项目的图像，该缩略图从上面的缩略图函数生成（在模板中，我使用product.mini_thumbnail，但似乎是知道图像？但是，如果我用我的MEDIA_URL打印product.image，然后我得到全图像。任何人都可以提出可能发生什么？

来源

2009-11-23 Udders

实际上是在得到MEDIA_ROOT创建缩略图？ img src网址是由模板生成的？ – rogueg 2009-11-23 17:13:19