ComputersProgramming

Parsing: what it is and how it is created

Very often on the Internet you can run into such a thing as "parsing". What is it and what is it for? It happens that programmers are given an assignment to sparzit a site. Or the average user encounters such a term and does not know its meaning.

Definition

If to take a general sense, then parsing is when a sequence of words is linearly compared with the rules of a particular language, which can be any human used in communication. It can also be a formalized language, for example, a programming language.

And regarding sites as an answer to questions about parsing - "what is it", "why is it used" - we can say that this is a process of sequential parsing of information that is placed on web pages. The text here is a set of data that is hierarchically organized and structured by computer and human language. The latter gives directly information, for which people come. And programming languages define ways of displaying this data on the user's monitor.

Content search

When the owner only creates his site, he faces a problem: where do you get the content to fill? The best option is to search the global network. Because there is a lot of knowledge. But then there are some difficulties:

  • Since the Internet is constantly growing and developing, it is clear that the site must contain huge amounts of information in order to have an advantage over competitors. There must be a lot of content today. And manually fill up with this amount of information the site is very difficult.
  • Since a person is not able to serve an endless stream of constantly changing information, parsing is necessary. What will it give? Automating the process of collecting information and changing it.

Pros of the parser

The program that performs the parsing process has several advantages in comparison with a human:

  • It will quickly go through thousands of Internet pages.
  • Without problems, he will share the technical data and information needed by the person.
  • Without errors, discard the unnecessary, leaving only what is needed.
  • Make the packing of data in the form necessary for the user.

Of course, the final result will still need some processing. It does not matter if it's a spreadsheet or a database. But this is much easier than if you do everything manually, and not use parsing. What this gives is quite clear - saving time and energy.

Development

A variety of programming languages are used to create parsers. The most common are scripting languages. This means that they are written scripts. What is a script and what is parsing done with the help of such languages will be considered further.

Creating a parser program does not require a serious knowledge of the programming language. Optional and fundamental information about technology. But I still need to know something. So, in order to know how to create parsing, that is, the analyzer program, you need to learn the following:

  • For the initial algorithm of the program functioning, careful analysis of the source code of the web page being the donor is needed. Here you can not do even without the average knowledge of imposition technologies. This is HTML, CSS and JavaScript.
  • To dive into the topic deeper, you need to learn the technology called DOM. It makes it possible to work very effectively with the hierarchy of a web page.
  • The most difficult stage is writing a parser. Here you need to own a tool for text processing. Experienced programmers often use regular expressions for this purpose, which are a powerful enough tool. But this is by far not every developer. Here you need special thinking. The optimal solution will be the use of ready-made libraries, which were created specifically for parsing. What are these libraries? This is a packed code that already contains all the functions for analysis.
  • It is very desirable to understand the object-oriented programming that is supported by any programming language.
  • The final stage of processing the results of the analysis assumes that the data will be structured and stored. Here you can not do without knowledge of databases.
  • You need knowledge and knowledge of the functions that are used to work with files. After all, the data will need to be written to these same files, and then, possibly, converted into a spreadsheet format.

Stages

If all requirements are met, then the further process can be divided into stages:

  1. At the first stage of parsing, the source code of the Internet page is obtained.
  2. The next step is extracting the necessary data from the markup code. Here an unnecessary code is discarded, all information is hierarchical.
  3. After successful processing of data, they must be stored in the form that can be further processed.
  4. Since the site consists not of one page, but of the set, the algorithm should be able to go to the next pages.

So, parsing - what is it? This is the process of analyzing the content of the site and isolating the necessary information. Using the above information, you can fill your sites with a lot of content automatically. And this gives an opportunity to gain time and win in the complex competition in the market for site builders.

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