In recent years, with the fire in the field of artificial intelligence, the language Python has gradually appeared in the mainstream view. Python has easy-to-understand syntax, concise writing, and a very rich library. It is an indispensable tool for the artificial intelligence and big data industries. Many friends have started to learn and are ready to enter the industry, so what knowledge do you need to know before learning crawler development?
1. Basic Principles of HTTP
Initiated by the client to the server, it can be divided into 4 parts: request method (Request Methon), request URL (Resquest URL), request header (Request Headers), and request body (Resquest Body).
1. There are two common request methods: GET and POST, as well as PUT, DELETE, HEAD and OPTIONS methods;
2. Request URL: URL, uniform resource locator, which can uniquely identify the resource we want;
3. Request header: It is used to describe the additional information to be used by the server. The more important information includes Cookie, Referer, User-Agent, etc.;
4. Request body: Generally, the carried content is the form data of a POST request, while for a GET request, the request body is empty.
2. Web page structure analysis
Web pages can be roughly divided into three parts-HTML (skeleton), CSS (skin) and JavaScript (muscle).
1. HTML: The language used to describe web pages, namely Hypertext Markup Language. Different elements are represented by different tags;
2. CSS: the full name of the stacked style sheet, is currently the only web page layout style standard;
3. JavaScript is a scripting language that realizes real-time, dynamic, and interactive page functions.
Three, the basic principles of crawlers
The crawler's workflow can be roughly divided into four steps: obtaining web pages, extracting information, saving data, and automating programs.
1. Get the webpage: get the source code of the webpage;
2. Extract information: analyze web content;
3. Save data: save to text or database;
4. Automated program: replace human operation.
Fourth, the choice of proxy IP
Proxy IP is one of the indispensable auxiliary tools in the crawler work process. Using proxy IP can make data collection more efficient and stable. It is recommended to use high-quality ** Tianqi IP proxy ** to assist crawlers. High-quality proxy IP meets several characteristics at the same time: large IP pool, fast IP speed, good IP stability, and high IP purity.