The web scraping is an easy as well a tricky concept to understand. This blog will helps you to know about the issue which are faced by the programmer while performing the web scraping.
What is Web Scraping?
The web scraping is a technique in which the data is extracted from the different website & online sources. It can be done either manually or automatic process. The manual scraping can generate the issue of the redundant data & also a very complicated process. And, for these automated web scraping is the perfect solution which provide a huge amount data that also in different format.
Web Scraping Process
The data scraping process are performed in the different stages-
- Visual Inspection
- The HTTP request is done for a web page
- Parsing the HTTP response
- Utilizing the relevant data
Initially different type of inbuilt browser toolsis used for searching the information across the web page& also finding their structure for scraping automatically.
The steps involve the systematically making the request for the webpagesas well as for implementing the scraping data logic by making use of pattern which identified. The fetched data are used for the respective purposes.
Web Scraping Difficulties
- Analysing the request rate
- Asynchronous loading
- Authentication
- Redirect & captcha
- Selecting the right libraries, framework & tools
- Inspection header
- Honeypots
- Pattern detection
- Resolving the complexities of python & web scraping
Many of the data tools are available for performing the web scraping using python. For simple websites scraping projects the grouping of the python request & the BeautifulSoup is the perfect solution. For the big size scraping projects, the use of Scrapy is beneficial.And, for the heavy JavaScript websites, they can be handled using the Selenium.
Authentication Handling
For the authentication, the cookies & the persist login must be preserved. And, the best option is to design a session, which can easily deal with all. For several unseen fields the manual login can be done & inspect the payload which are sent to the server using several network tools provided by the browser to recognize the secret data which is sent.
The review can also be done of what the header are sending to the server by using browsers tools. So that we can easily replicate the behaviour in the following code. And, if the website has any cookies based authentication, the cookies code can also be copied & be added to the scraper code.
Asynchronous Loading Handling
The asynchronous loading can be identified while the visual inspection by viewing the page source& also in the content we are searching for. If the text is absent in the source & is still visible in the browser than it might be due to the rendered JavaScript. The additional inspection is required in that case using the browser tool network for reviewing the all request which are made by the website.
Bypassing Asynchronous Loading
Web Driver Usage
The web driver usage is like a simulation of web browsers with interfaces in order get control using the scripts. It can perform the rendering JavaScript, Organizing the session & cookies, etc. selenium web drivers is a type of automation framework are designed to test UI/UX of websites. And, is the most common option to scrap dynamic rendered websites.
Inspecting AJAX Calls
It mainly works on the idea, that if anything is displayed on browser than it has to come from somewhere. We can use the browser developer tools for inspecting the AJAX Calls& also help in determining the request for data fetching which we have been searching for. We can set the X-Requested with the header for AJAX request in the script.
Tackle Infinite Scrolling
We can tackle with the infinite scrolling by combining the JavaScript logic in Selenium. And, the infinite scrolling comprises of the more AJAX calls to servers that can be easily inspected using the different browser tools & replicating them in the programs.
Getting Perfect Selector
When we locate the visual which are to be scraped than consider the following steps for discovering the selector pattern for the elements. The element can be easily filtered depending upon the attributes & CSS Classes.
The CSS selector are the prime choice while scraping. The alternative for it is the XPath, which can be used in more scenario & is more flexible.
Captcha & Redirect Handling
The contemporary libraries take care of the request of HTTP redirects as well returning to the final page. Scrapy has the redirect middleware which can easily handle this redirect. When this redirect are made to the page we are seeking they don’t cause any trouble, but if they redirected to the captcha than many issue can be raised.
OCR can be used for solving the, text based captcha& makes their handling an easy process.
Unstructured Responses & iframe Tags Handling
For the different iframe tags, the request for the right URL can be done to get the data back. First, we request the outer page & then get the iframe. And, then another HTTP request is done to get the Iframe SRC Attributes.
The web scraping sound easy, but it become very complicated when is not done by the experts. It may also result in the copyright violation & information abuse usage can cause legal consequences. So, if you want the Expertise Python Web Scraping Service than approach LogicWis without any second thought.