Scraping PDF documents and HTML files with regular expressions

23.05.2018

Scraping PDF documents and HTML les with regular expressions

The regular expression is a sequence of characters that de ne the search pattern and used to scrape data on the net. They are mainly used by search engines and can remove the unnecessary dialogs of text editors and word processors. A regular expression known as Web Pattern speci es the sets of a string. It acts as a powerful framework and is capable of scraping data from different web pages. The regular expression consists of web and HTML constants, and operator symbols. There are 14 different characters and meta-characters based on the regex processor. These characters along with metacharacters help scrape data from dynamic websites.

There are a large number of software and tools that can be used to download web pages and extract information from them. If you want to download data and process it in a desirable format, you can opt for regular expressions.

Index your websites and scrape data: There are chances that your web scraper will not work ef ciently and won't be able to download copies of les comfortably. In such circumstances, you should use regular expressions and get your data scraped. Besides, regular expressions will make it easy for you to convert unstructured data into a readable and scalable form. If you are looking to index your web pages, regular expressions are the right choice for you. They will not only scrape data from websites and blogs but also help you crawl your web documents. You don't need to learn any other programming languages such as Python, Ruby, and C++.

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23.05.2018

Before you start data extraction with regular expressions, you should make a list of the URLs you want to scrape data from. If you cannot properly recognize web documents, you may try Scrapy or BeautifulSoup to get your work done. And if you have already made the list of URLs, then you can immediately start working with regular expressions or another similar framework.

PDF documents: You can also download and scrape PDF les using speci c regular expressions. Before you opt for a scraper, make sure you have converted all PDF documents to text les. You can also transform your PDF les into the RCurl package and use different command line tools such as Libcurl and Curl. RCurl cannot handle the webpage with HTTPS directly. It means that website URLs containing HTTPS might not work properly with regular expressions.

HTML les: Websites that contain complicated HTML codes cannot be scraped with a traditional web scraper. Regular expressions not only help scrape HTML les but also target different PDF documents, images, audio and video les.

They make it easy for you to collect and extract data in a readable and scalable form. Once you have scraped the data, you should create different folders and get your data saved in those folders. Rvest is a comprehensive package and a good alternative to Import.io. It can scrape data from the HTML pages. Its options and features are inspired by BeautifulSoup. Rvest works with Magritte and can bene t you in the absence of a regular expression. You can perform complex data scraping tasks with Rvest.

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