我正在尝试将抓取的项目保存在单独的json文件中，但没有看到任何输出文件。管道和项目在scrapy项目文件夹中的piplines.py和items.py文件中定义。我必须显式调用process_item（）还是在scrape（）返回项时自动调用它？我在CrawlerProcess（settings = {'ITEM_PIpelInes'}）中启用了管道。谢谢。

管道

data1 = rnorm(10000,mean=8,sd=1.3)
data2 = rnorm(10000,mean=4,sd=1.0)

#plot data1 histogram with 40 bins
hist(data1,breaks=40,col="red",xlim=c(2,14),ylim=c(0,800),main="Gaussian deviates :  mean=8,sigma=1.3",col.main="blue")
segments(quantile(data1,0.25),quantile(data1,600,col="green",lwd=4,lty=1)

#plot data2 histogram with 40 bins
hist(data2,900),main="Gaussian deviates :  mean=4,sigma=1.0",col.main="blue")
print(quantile(data1,0.25))

import json,datetime

class JsonWriterPipeline(object):
    def process_item(self,item,spider):
        # return item
        fileName = datetime.datetime.now().strftime("%Y%m%d%H%M%S") + '.json'
        try:
            with open(fileName,'w') as fp:
                json.dump(dict(item),fp)
                return item
        except:
            return item

class ProjectItem(scrapy.Item):
   title = scrapy.Field()
   url = scrapy.Field()