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Step-by-step Guide to Build a Web Crawler for Beginners

Friday, July 1, 2022

As a newbie, I built a web crawler and successfully extracted 20k data from the Amazon Career website. Want to know how to make a web crawler and create a database that eventually turns into your asset at no cost? This article will share with you the different ways including coding and no-coding ways step-by-step.

 

What Is A Web Crawler

A web crawler is an internet bot that indexes the content of websites. It can automatically extract target information and data from websites and export data into structured formats (list/table/database). Here is a video that explain the web crawler and the difference between web crawlers and web scrapers.

 

 

You may be curious about is web crawler legal or not, well, it depends. But generally speaking, it's totally legal in most countries to crawl the public data on a website.

 

Why Do You Need A Web Crawler

Imagine a world without Google Search. How long do you think it will take to get a recipe for chicken nuggets from the Internet? There are 2.5 quintillion bytes of data being created online each day. Without search engines like Google, it will be like looking for a needle in a haystack.

website database

From Hackernoon by Ethan Jarrell

 

A search engine is a unique kind of web crawler that indexes websites and finds web pages for us. Besides search engines, you can also build a customized web crawler to help you achieve:

1. Content aggregation: It works to compile information on niche subjects from various resources into one single platform. As such, it is necessary to crawl popular websites to fuel your platform in time.

2. Sentiment analysis: It is also called opinion mining. As the name indicates, it is the process to analyze public attitudes toward one product and service. It requires a monotonic set of data to evaluate accurately. A web crawler can extract tweets, reviews, and comments for analysis.

3. Lead generation: Every business needs sales leads. That's how they survive and prosper. Let's say you plan to make a marketing campaign targeting a specific industry. You can scrape email, phone number, and public profiles from an exhibitor or attendee list of Trade Fairs, like attendees of the 2018 Legal Recruiting Summit.

 

How to Build A Web Crawler with Coding Script

Writing scripts with computer languages is predominantly used by programmers. It can be as powerful as you create it to be. Here is an example of a snippet of bot code.

 build a web crawler by coding

 From Kashif Aziz

3 Steps to Build A Web Crawler Using Python

Step 1: Send an HTTP request to the URL of the webpage. It responds to your request by returning the content of web pages.

Step 2: Parse the webpage. A parser will create a tree structure of the HTML as the webpages are intertwined and nested together. A tree structure will help the bot follow the paths that we created and navigate through to get the information.

Step 3: Using the Python library to search the parse tree.

Among the computer languages for a web crawler, Python is easy-to-implement compared to PHP and Java. It still has a steep learning curve that prevents many non-tech professionals from using it. Even though it is an economic solution to write your own, it's still not sustainable with regard to the extended learning cycle within a limited time frame.

 

No-Coding Web Crawler Tool for Free

If you don't want to learn to code, you can try to use web scraping tools on the market. Here we recommend Octoparse, which is a free web crawler maker and no requirements for coding. Download and install it on your Windows/Mac devices, and follow the easy steps below.

How to Free Create A Web Crawler with Octoparse No Coding

Step 1. Open Octoparse and paste the target URL on the main panel, it will begin detecting automatically. Or you can select the "Advanced Mode" to try more customized options.

Step 2. You can simply preview the data is detected, and click the "Create workflow" button to set the crawler. You can customize the data field as you need by clicking the target data position with the tips. Octoparse supports setting up pagination by clicking the "Next Page" button so that the crawler can navigate through it.

Step 3. Once you finish setting up the extraction fields, click the "Run" button to execute the crawler. You can download the data to local devices by Excel or CVS.

 

If you still have questions, move to the user guide to learn more details. Octoparse also provides Task Templates that cover over 30 websites for starters to grow comfortable at the beginning. These templates allow users to capture the data without task configuration and are extremely beginner-friendly.

 

Conclusion

Writing scripts can be painful as it has high initial and maintenance costs. No single web page is identical, and we need to write a script for every single site. It is not sustainable if you need to crawl many different websites. Besides, websites tend to change layouts and structures after a period of time. As a result, we have to debug and adjust the crawler accordingly. A web crawler tool like Octoparse is more practical for enterprise-level data extraction with fewer efforts and lower costs.

octoparse vs python web crawling

 

Related Resources

Top 20 Web Crawling Tools for Extracting Web Data

Free Online Web Crawler Tools

9 FREE Web Scrapers That You Cannot Miss

Creating a Simple Web Crawler in PHP

Is Web Crawling Legal

What Is a Web Crawler and How Does It Work

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