scrapy pipelines导出各种格式

scrapy在使用pipelines的时候，我们经常导出csv,json.jsonlines等等格式。每次都需要写一个类去导出，很麻烦。

这里我整理一个pipeline文件，支持多种格式的。

# -*- coding: utf-8 -*-

# Define your item pipelines here
#
# Don‘t forget to add your pipeline to the ITEM_PIPELINES setting
# See: http://doc.scrapy.org/en/latest/topics/item-pipeline.html

from scrapy import signals
from scrapy.exporters import *

class BaseExportPipeLine(object):
    def __init__(self,exporter,dst):
        self.files = {}
        self.exporter=exporter
        self.dst=dst
    @classmethod
    def from_crawler(cls, crawler):
        pipeline = cls()
        crawler.signals.connect(pipeline.spider_opened, signals.spider_opened)
        crawler.signals.connect(pipeline.spider_closed, signals.spider_closed)
        return pipeline

    def spider_opened(self, spider):
        file = open(self.dst, ‘wb‘)
        self.files[spider] = file
        self.exporter = self.exporter(file)
        self.exporter.start_exporting()

    def spider_closed(self, spider):
        self.exporter.finish_exporting()
        file = self.files.pop(spider)
        file.close()

    def process_item(self, item, spider):
        self.exporter.export_item(item)
        return item
class JsonExportPipeline(BaseExportPipeLine):
    def __init__(self):
        super(JsonExportPipeline, self).__init__(JsonItemExporter,"items.json")
class JsonLinesExportPipeline(BaseExportPipeLine):
    def __init__(self):
        super(JsonLinesExportPipeline, self).__init__(JsonLinesItemExporter,"items.jl")
class XmlExportPipeline(BaseExportPipeLine):
    def __init__(self):
        super(XmlExportPipeline, self).__init__(XmlItemExporter,"items.xml")
class CsvExportPipeline(BaseExportPipeLine):
    def __init__(self):
        super(CsvExportPipeline, self).__init__(CsvItemExporter,"items.csv")
class  PickleExportPipeline(BaseExportPipeLine):
    def __init__(self):
        super(PickleExportPipeline, self).__init__(PickleItemExporter,"items.pickle")
class  MarshalExportPipeline(BaseExportPipeLine):
    def __init__(self):
        super(MarshalExportPipeline, self).__init__(MarshalItemExporter,"items.marsha")
class  PprintExportPipeline(BaseExportPipeLine):
    def __init__(self):
        super(PprintExportPipeline, self).__init__(PprintItemExporter,"items.pprint.jl")

上面的定义好之后。我们就可以在settings.py里面设置导出指定的类了。是不是很强大。