Basic tutorial for Scrapy [Scraping framework]


Scrapy is scrapying OSS tool for extracting the data you need from websites. In addition, Scrapy Cloud - Scrapyinghub is a powerful and useful platform to run Scrapy cralwer. This article describes basic tutorial for Scrapy.

🐠 Installation

Install Scrapy and Scrapyinghub library at the first time:

pip install scrapy shub

After then, please create a new project for Scrapy:

scrapy startproject PROJECT_NAME
cd PROJECT_NAME

🎳 Create Spider

In scrapy, you create some spiders which is crawler in a project. You can create the spider by the following command:

# Generate code to scrape a new site
scrapy genspider blogsider blog.scrapinghub.com

After the above command, please change spiders/blogsider.py:

import scrapy

class BlogSpider(scrapy.Spider):
    name = 'blogspider'
    allowed_domains = ['blog.scrapinghub.com']
    start_urls = ['https://blog.scrapinghub.com']

    def parse(self, response):
        for title in response.css('h2.entry-title'):
            yield {'title': title.css('a ::text').extract_first()}

        for next_page in response.css('div.prev-post > a'):
            yield response.follow(next_page, self.parse)

So, your spider can get title in entry list.

🐝 Run the cawler in local

You can execute your crawler on local:

# Execute scraping in local
scrapy crawl blogspider

😎 Get API Key on Scrapinghub

If you create an account on Scrapy Cloud - Scrapyinghub, you can deloy your code to there and execute it on theere.

After creating the account, please create project and confirm API key and Project Id.

🗻 Create Scrapyinghub Configuration

Create scrapinghub.yml:

projects:
  default: YOUR_PROJECT_ID
stack: scrapy:1.5-py3

Please set your project id and stack information which you want to use. If you want to know more detail of stack information, please see shub/deploying.

🐰 Deploy to Scrapyinghub

Let’s deply your code to Scrapyinghub with the API key:

# Install a library for scrapying hub
pip install shub

# Logging in Scrapinghub with 
shub login

# Deploy to Scrapinghub
shub deploy # Deploy the spider to Scrapy Cloud

# Execute spider on Scrapinghub
shub schedule blogspider

After then, you can confirm the result items by Scrapyinghub screen.

🐡 How to access settings

print("Existing settings: %s" % self.settings.attributes.keys())

If you want to know more detail, please see https://doc.scrapy.org/en/latest/topics/settings.html .

🎂 Appendix

Scrapy Cloud API

Scrapy Cloud on Scrapyinghub has useful API. Please confirm as follows:

https://doc.scrapinghub.com/scrapy-cloud.html

Downloading and processing files and images

Scrapy provides reusable item pipelines for downloading files attached to a particular item.

  • Download their images
  • Create thumbnail

If you want to know more detail, please see official document: Downloading and processing files and images.

Scrapy Configuration

About settings.py:

  • DEPTH_LIMIT : Depth to scrape
  • DOWNLOAD_DELAY : Intervals for downloading data in scraping

Sentry

Installation

pip install scrapy-sentry

Configuration

# sentry dsn
SENTRY_DSN = 'http://public:secret@example.com/1'
EXTENSIONS = {
    "scrapy_sentry.extensions.Errors":10,
}

Addons

Magic Fields

Monitoring

  • Monitor spiders and item validation check
  • Enable to define scrapy stats values
  • Get email and slack notifications

DotScrapy Persistence

  • Allows the crawler to access a persistent storage and share data among different runs of a spider by S3
  • It ignore duplicated URL among some jobs of a spider.
  • It is difficult to recover error sometimes, so please be careful to use it.

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