Very often on the Internet you can come across a concept such as "parsing". What is it and what is it for? It happens that programmers are given the task to parse a website. Or an ordinary user encounters such a term and does not know its meaning.
Definition
If we take the general meaning, then parsing is when the 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, such as a programming language.
As regards 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 the information that is posted on web pages. The text here is a data set that is hierarchically ordered and structured using computer and human language. The latter gives directly information for which people come. And programming languages determine how to display this data on the user's monitor.
Content Search
When the owner just creates his site, he faces a problem: where to get the content to fill out? The best option is to search the global network. After all, there is infinitely much knowledge. But there are also 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. Today there should be a lot of content. And manually filling this amount of information into a website 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? Automation of the process of collecting information and its changes.
Parser Pros
A program implementing the parsing process, in comparison with a person, has several advantages:
- It will quickly go through thousands of web pages.
- Without problems, it will separate technical data and information that a person needs.
- Without errors, it will reject the unnecessary, leaving only what is necessary.
- Will pack the data in the form necessary for the user.
Of course, the final result will still need some processing. And it doesn’t matter if it is a spreadsheet or a database. But this is already much easier than if you do everything manually, rather than using parsing. What this gives is quite clear - saving time and effort.
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 carried out using such languages will be discussed later.
Creating a parser program does not require serious knowledge of a programming language. Fundamental technology information is also optional. But you still need to know something. So, to know how to create parsing, that is, an analyzer program, you need to learn the following:
- The initial algorithm of the program’s functioning requires a thorough analysis of the source code of the donor web page. Here you can not do without at least an average knowledge of layout technologies. These are HTML, CSS and JavaScript.
- To dive deeper into the topic, you need to study a 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 word processing tool. Experienced programmers most often use regular expressions for this purpose, which are quite a powerful tool. But not every developer can do it. Here you need special thinking. The best solution would be to use ready-made libraries that were created specifically for parsing. What are these libraries? This is packaged code that already contains all the functions for analysis.
- It is highly advisable to understand object-oriented programming, which is supported by any programming language.
- The final stage of processing the analysis results assumes that the data will be structured and stored. Here you can not do without knowledge of databases.
- Need knowledge and knowledge of the functions used to work with files. After all, the data will need to be written into these very files, and then, possibly, converted to a spreadsheet format.
Stages
If all the requirements are met, then the further process can be divided into stages:
- At the first stage of parsing, the source code of the web page is received.
- The next step is to extract the necessary data from the markup code. Unnecessary code is discarded here, all information is arranged in a hierarchy.
- After successful processing of the data, they must be saved in the form that can be further processed.
- Since the site does not consist of one page, but of many, the algorithm should be able to go to subsequent 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 makes it possible to buy time and win in difficult competition in the site builders market.