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我只需要了解如何检测scrapy是否保存和蜘蛛中的项目？我正在从一个站点获取项目，然后我正在获取对该项目的评论。所以首先我必须保存项目，然后我会保存评论。但是当我在 yield 之后编写代码时，它给了我这个错误。

save() prohibited to prevent data loss due to unsaved related object ''.

这是我的代码

def parseProductComments(self, response):

        name = response.css('h1.product-name::text').extract_first()
        price = response.css('span[id=offering-price] > span::text').extract_first()
        node = response.xpath("//script[contains(text(),'var utagData = ')]/text()")
        data = node.re('= (\{.+\})')[0]  #data = xpath.re(" = (\{.+\})")
        data = json.loads(data)

        barcode = data['product_barcode']

        objectImages = []
        for imageThumDiv in response.css('div[id=productThumbnailsCarousel]'):
            images = imageThumDiv.xpath('img/@data-src').extract()
            for image in images:
                imageQuality = image.replace('/80/', '/500/')
                objectImages.append(imageQuality)
        company = Company.objects.get(pk=3)
        comments = []
        item = ProductItem(name=name, price=price, barcode=barcode, file_urls=objectImages, product_url=response.url,product_company=company, comments = comments)
        yield item
        print item["pk"]
        for commentUl in response.css('ul.chevron-list-container'):

            url = commentUl.css('span.link-more-results::attr(href)').extract_first()
            if url is not None:
                for commentLi in commentUl.css('li.review-item'):
                    comment = commentLi.css('p::text').extract_first()
                    commentItem = CommentItem(comment=comment, product=item.instance)

                    yield commentItem
            else:

                yield scrapy.Request(response.urljoin(url), callback=self.parseCommentsPages, meta={'item': item.instance})

这是我的管道。

def comment_to_model(item):
    model_class = getattr(item, 'Comment')
    if not model_class:
        raise TypeError("Item is not a `DjangoItem` or is misconfigured")

def get_comment_or_create(model):
    model_class = type(model)
    created = False
    # Normally, we would use `get_or_create`. However, `get_or_create` would
    # match all properties of an object (i.e. create a new object
    # anytime it changed) rather than update an existing object.
    #
    # Instead, we do the two steps separately
    try:
        # We have no unique identifier at the moment; use the name for now.
        obj = model_class.objects.get(product=model.product, comment=model.comment)
    except model_class.DoesNotExist:
        created = True
        obj = model  # DjangoItem created a model for us.
        obj.save()

    return (obj, created)

def get_or_create(model):
    model_class = type(model)
    created = False
    # Normally, we would use `get_or_create`. However, `get_or_create` would
    # match all properties of an object (i.e. create a new object
    # anytime it changed) rather than update an existing object.
    #
    # Instead, we do the two steps separately
    try:
        # We have no unique identifier at the moment; use the name for now.
        obj = model_class.objects.get(product_company=model.product_company, barcode=model.barcode)
    except model_class.DoesNotExist:
        created = True
        obj = model  # DjangoItem created a model for us.
        obj.save()

    return (obj, created)


def update_model(destination, source, commit=True):
    pk = destination.pk

    source_dict = model_to_dict(source)
    for (key, value) in source_dict.items():
        setattr(destination, key, value)

    setattr(destination, 'pk', pk)

    if commit:
        destination.save()
    return destination


class ProductItemPipeline(object):
    def process_item(self, item, spider):
        if isinstance(item, ProductItem):
            item['cover_photo'] = item['files'][0]['path']
            item_model = item.instance
            model, created = get_or_create(item_model)
            #update_model(model, item_model)

            if created:
                for image in item['files']:
                    imageItem = ProductImageItem(image=image['path'], product=item.instance)
                    imageItem.save()
                # for comment in item['comments']:
                #     commentItem = CommentItem(comment=comment, product= item.instance)
                #     commentItem.save()
            return item
        if isinstance(item, CommentItem):
            comment_to_model = item.instance
            model, created = get_comment_or_create(comment_to_model)
            if created:
                print model
            else:
                print created
            return item
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1 回答 1

1

获取或创建

您的大部分代码似乎都在处理 get_or_create 的明显弱点

# Normally, we would use `get_or_create`. However, `get_or_create` would
# match all properties of an object (i.e. create a new object
# anytime it changed) rather than update an existing object.

幸运的是，这个明显的缺点可以很容易地克服。感谢get_or_create的默认参数

传递给 get_or_create() 的任何关键字参数——除了一个称为默认值的可选参数——将在 get() 调用中使用。如果找到一个对象，get_or_create() 将返回该对象的元组和 False。如果找到多个对象，get_or_create 将引发 MultipleObjectsReturned。如果找不到对象，get_or_create() 将实例化并保存一个新对象，返回一个新对象的元组和 True。

更新或创建

仍然不相信 get_or_create 是这份工作的合适人选？我也不是。还有更好的东西。更新或创建！

一种使用给定 kwargs 更新对象的便捷方法，必要时创建一个新对象。默认值是用于更新对象的 (field, value) 对的字典。

但我不会详述 update_or_create 的用户，因为您的代码中尝试更新模型的行已被注释掉，并且您没有明确说明要更新的内容。

新管道

使用标准 API 方法，包含管道的模块只需简化为 ProductItemPipeline 类。并且可以修改

class ProductItemPipeline(object):
    def process_item(self, item, spider):
        if isinstance(item, ProductItem):
            item['cover_photo'] = item['files'][0]['path']

            model, created = ProductItem.get_or_create(product_company=item['product_company'], barcode=item['bar_code'], 
    defaults={'Other_field1': value1, 'Other_field2': value2})

            if created:
                for image in item['files']:
                    imageItem = ProductImageItem(image=image['path'], product=item.instance)
                    imageItem.save()
            return item

        if isinstance(item, CommentItem):

            model, created = CommentItem.get_or_create(field1=value1, defaults={ other fields go in here'})

            if created:
                print model
            else:
                print created
            return item

原始代码中的错误

我确实相信这是存在错误的地方。

  obj = model_class.objects.get(product=model.product, comment=model.comment)

现在我们没有使用它，所以这个错误应该消失了。如果您仍有问题，请粘贴完整的回溯。

于 2017-01-07T06:03:43.243 回答