Basic process of web crawler

The basic process of a web crawler: 1. Determine the target and select one or more websites or web pages; 2. Write code and use a programming language to write the web crawler code; 3. Simulate browser behavior and use HTTP Request to access the target website; 4. Parse the web page and parse the HTML code of the web page to extract the required data; 5. Store the data and save the obtained data to the local disk or database.

Web crawler, also called web spider. Web crawler, also called web spider or web robot, is an automated program used to automatically crawl the Internet. data. Web crawlers are widely used in search engines, data mining, public opinion analysis, business competitive intelligence and other fields. So, what are the basic steps of a web crawler? Next, let me introduce it to you in detail.

When we use a web crawler, we usually need to follow the following steps:

1. Determine the target

We need to select one or more websites Or a web page to obtain the required data. When selecting a target website, we need to consider factors such as the website's theme, structure, and type of target data. At the same time, we must pay attention to the anti-crawler mechanism of the target website and pay attention to avoidance.

2. Write code

We need to use a programming language to write the code of the web crawler in order to obtain the required data from the target website. When writing code, you need to be familiar with web development technologies such as HTML, CSS, and JavaScript, as well as programming languages ​​such as Python and Java.

3. Simulate browser behavior

We need to use some tools and technologies, such as network protocols, HTTP requests, responses, etc., in order to communicate with the target website, and Get the required data. Generally, we need to use HTTP requests to access the target website and obtain the HTML code of the web page.

4. Parse the web page

Parse the HTML code of the web page to extract the required data. Data can be in the form of text, pictures, videos, audio, etc. When extracting data, you need to pay attention to some rules, such as using regular expressions or XPath syntax for data matching, using multi-threading or asynchronous processing technology to improve the efficiency of data extraction, and using data storage technology to save data to a database or file system.

5. Store data

We need to save the obtained data to the local disk or database for further processing or use. When storing data, you need to consider data deduplication, data cleaning, data format conversion, etc. If the amount of data is large, you need to consider using distributed storage technology or cloud storage technology.

Summary:

The basic steps of a web crawler include determining the target, writing code, simulating browser behavior, parsing web pages and storing data. These steps may vary when crawling different websites and data, but no matter which website we crawl, we need to follow these basic steps to successfully obtain the data we need.

The above is the detailed content of Basic process of web crawler. For more information, please follow other related articles on the PHP Chinese website!