How to Build a Web Crawler – A Guide for Beginners
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Why do you need a Web Crawler, especially for Enterprises?
Imagine Google Search doesn't exist. How long will it take you to get the recipe for chicken nuggets without typing in the keyword? There are 2. 5 quintillion bytes of data created each day. That said, without Google Search, it's impossible to find the information.
From Hackernoon by Ethan Jarrell
Google Search is a unique web crawler that indexes the websites and finds the page for us. Besides the search engine, you can build a 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 towards 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 as a beginner?
A. Scraping with a programming language
writing scripts with computer languages are 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.
From Kashif Aziz
Web scraping using Python involves three main steps:
1. Send an HTTP request to the URL of the webpage. It responds to your request by returning the content of web pages.
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.
3. Using python library to search the parse tree.
Among the computer languages for a web crawler, Python is easy-to-implement comparing 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 regard to the extended learning cycle within a limited time frame.
However, there is a catch! What if there is a method that can get you the same results without writing a single line of code?
B. Web scraping tool comes in handy as a great alternative.
There are many options, but I use Octoparse. Let's go back to the Amazon Career webpage as an example:
Goal: build a crawler to extract administrative job opportunities including Job title, Job ID, description, basic qualification, preferred qualification, and page URL.
URL:
1. Open Octoparse and select "how to write a web crawler in python,free web crawler,web crawler example,python web crawler source code,open source web crawler,web crawler tool,web crawling vs web scraping,web crawler online")
how to write a web crawler in python,free web crawler,web crawler example,python web crawler source code,open source web crawler,web crawler tool,web crawling vs web scraping,web crawler online
How do I create a web crawler?
Design a web crawlerStep 1: Outline use cases and constraints. Gather requirements and scope the problem. … Step 2: Create a high level design. Outline a high level design with all important components.Step 3: Design core components. Dive into details for each core component. … Step 4: Scale the design.
What is a web crawler Python?
A web crawler is nothing but a few lines of code. This program or code works as an Internet bot. The task is to index the contents of a website on the internet. Now we know that most web pages are made and described using HTML structures and keywords.Aug 12, 2020
What is Web crawling and scraping in Python?
