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SimpleCrawler

A simple web crawler developed upon scrapy with some degree of extensibility.

Brief Introduction

The crawler is able to handle this simplest use case:

  • target webpages are linearly constructed, which means there is no need to crawl a subpage.
  • given a webpage, it can be determined that whether the crawling process should continue.
  • given a webpage, url to next page, if any, can be determined.

A sample parser which crawls basic project information from https://pro.lagou.com/project/kaifa is included in the source (at SimpleCrawler/cores/dakun.py). Theoretically any module that conforms to following prototype would work.

  • lays in the folder cores
  • has a class Page in it
  • the class Page can be constructed with a scrapy.Response
  • the class Page should have a static variable start_url holds the url of starting page.
  • An instance of class Page should have:
    • a has_next field indicates whether the crawling process should continue
    • a next field holds an url of next page, if any.
    • an output field holds a piece of record as dict

Usage

scrapy crawl simple -a core=<website_parser_module> -o <output_file_name>.<json|cvs|jl|xml> [-L INFO]

-L INFO is to eliminate the verbose DEBUG logging, if the logging level is set to DEBUG(default value) all exports would be logged.

jl stands for json line. The difference between file.jl and file.json can be briefly stated that jl file contains a bunch of json objects as seperate lines while json joins them as an array of objects. jl file may be found convinent for incremental recording while 'json' is easy to read by existing json decoders. more information in scrapy docs

for example:

scrapy crawl simple -a core=dakun -o o.json -L INFO

dakun can be changed to any compatible parser.