我在一个网络抓取项目中使用MongoEngine.我想跟踪我在所有抓取的网页上遇到的所有图像.
为此,我存储图像src URL和图像遇到的次数.
MongoEngine模型定义如下：
class ImagesUrl(Document):
""" Model representing images encountered during web-scraping.
When an image is encountered on a web-page during scraping,we store its url and the number of times it has been
seen (default counter value is 1).
If the image had been seen before,we do not insert a new document
in collection,but merely increment the corresponding counter value.
"""
# The url of the image. There cannot be any duplicate.
src = URLField(required=True,unique=True)
# counter of the total number of occurences of the image during
# the datamining process
counter = IntField(min_value=0,required=True,default=1)
我正在寻找实现“保存或增量”过程的正确方法.
到目前为止,我正在以这种方式处理它,但我觉得可能有更好的,内置的方式使用MongoEngine：
def save_or_increment(self):
""" If it is the first time the image has been encountered,insert
its src in mongo,along with a counter=1 value.
If not,increment its counter value by 1.
"""
# check if item is already stored
# if not,save a new item
if not ImagesUrl.objects(src=self.src):
ImagesUrl(
src=self.src,counter=self.counter,).save()
else:
# if item already stored in Mongo,just increment its counter
ImagesUrl.objects(src=self.src).update_one(inc__counter=1)
有没有更好的方法呢？
非常感谢您的宝贵时间.
解决方法
你应该能够做一个
upsert,例如：
ImagesUrl.objects(src=self.src).update_one(
upsert=True,inc__counter=1,set__src=self.src)