Solblog109

1. Web Scraping With Selenium Python
2. Selenium For Web Scraping

Introduction to Web Scraping using Selenium. In this tutorial we will build a web scraping program that will scrape a Github user profile and get the Repository Names and the Languages for the. Aug 30, 2020 What is Selenium: – Selenium is an open-source web-based automation tool. Selenium primarily used for testing in the industry but It can also be used for web scraping. We’ll use the Chrome browser but you can try on any browser, It’s almost the same. Now let us see how to use selenium for Web Scraping.

In the last tutorial we learned how to leverage the Scrapy framework to solve common web scraping problems.Today we are going to take a look at Selenium (with Python ❤️ ) in a step-by-step tutorial.

Selenium refers to a number of different open-source projects used for browser automation. It supports bindings for all major programming languages, including our favorite language: Python.

The Selenium API uses the WebDriver protocol to control a web browser, like Chrome, Firefox or Safari. The browser can run either localy or remotely.

At the beginning of the project (almost 20 years ago!) it was mostly used for cross-browser, end-to-end testing (acceptance tests).

Now it is still used for testing, but it is also used as a general browser automation platform. And of course, it us used for web scraping!

Selenium is useful when you have to perform an action on a website such as:

• Clicking on buttons
• Filling forms
• Scrolling
• Taking a screenshot

It is also useful for executing Javascript code. Let's say that you want to scrape a Single Page Application. Plus you haven't found an easy way to directly call the underlying APIs. In this case, Selenium might be what you need.

Installation

We will use Chrome in our example, so make sure you have it installed on your local machine:

• selenium package

To install the Selenium package, as always, I recommend that you create a virtual environment (for example using virtualenv) and then:

Quickstart

Once you have downloaded both Chrome and Chromedriver and installed the Selenium package, you should be ready to start the browser:

This will launch Chrome in headfull mode (like regular Chrome, which is controlled by your Python code).You should see a message stating that the browser is controlled by automated software.

To run Chrome in headless mode (without any graphical user interface), you can run it on a server. See the following example:

The driver.page_source will return the full page HTML code.

Here are two other interesting WebDriver properties:

• driver.title gets the page's title
• driver.current_url gets the current URL (this can be useful when there are redirections on the website and you need the final URL)

Locating Elements

Locating data on a website is one of the main use cases for Selenium, either for a test suite (making sure that a specific element is present/absent on the page) or to extract data and save it for further analysis (web scraping).

There are many methods available in the Selenium API to select elements on the page. You can use:

• Tag name
• Class name
• IDs
• XPath
• CSS selectors

We recently published an article explaining XPath. Don't hesitate to take a look if you aren't familiar with XPath.

As usual, the easiest way to locate an element is to open your Chrome dev tools and inspect the element that you need.A cool shortcut for this is to highlight the element you want with your mouse and then press Ctrl + Shift + C or on macOS Cmd + Shift + C instead of having to right click + inspect each time:

find_element

There are many ways to locate an element in selenium.Let's say that we want to locate the h1 tag in this HTML:

All these methods also have find_elements (note the plural) to return a list of elements.

For example, to get all anchors on a page, use the following:

Some elements aren't easily accessible with an ID or a simple class, and that's when you need an XPath expression. You also might have multiple elements with the same class (the ID is supposed to be unique).

XPath is my favorite way of locating elements on a web page. It's a powerful way to extract any element on a page, based on it's absolute position on the DOM, or relative to another element.

WebElement

A WebElement is a Selenium object representing an HTML element.

There are many actions that you can perform on those HTML elements, here are the most useful:

• Accessing the text of the element with the property element.text
• Clicking on the element with element.click()
• Accessing an attribute with element.get_attribute('class')
• Sending text to an input with: element.send_keys('mypassword')

There are some other interesting methods like is_displayed(). This returns True if an element is visible to the user.

It can be interesting to avoid honeypots (like filling hidden inputs).

Honeypots are mechanisms used by website owners to detect bots. For example, if an HTML input has the attribute type=hidden like this:

This input value is supposed to be blank. If a bot is visiting a page and fills all of the inputs on a form with random value, it will also fill the hidden input. A legitimate user would never fill the hidden input value, because it is not rendered by the browser.

That's a classic honeypot.

Full example

Here is a full example using Selenium API methods we just covered.

We are going to log into Hacker News:

In our example, authenticating to Hacker News is not really useful on its own. However, you could imagine creating a bot to automatically post a link to your latest blog post.

In order to authenticate we need to:

• Go to the login page using driver.get()
• Select the username input using driver.find_element_by_* and then element.send_keys() to send text to the input
• Follow the same process with the password input
• Click on the login button using element.click()

Should be easy right? Let's see the code:

Easy, right? Now there is one important thing that is missing here. How do we know if we are logged in?

We could try a couple of things:

• Check for an error message (like “Wrong password”)
• Check for one element on the page that is only displayed once logged in.

So, we're going to check for the logout button. The logout button has the ID “logout” (easy)!

We can't just check if the element is None because all of the find_element_by_* raise an exception if the element is not found in the DOM.So we have to use a try/except block and catch the NoSuchElementException exception:

Taking a screenshot

We could easily take a screenshot using:

Note that a lot of things can go wrong when you take a screenshot with Selenium. First, you have to make sure that the window size is set correctly.Then, you need to make sure that every asynchronous HTTP call made by the frontend Javascript code has finished, and that the page is fully rendered.

In our Hacker News case it's simple and we don't have to worry about these issues.

Waiting for an element to be present

Dealing with a website that uses lots of Javascript to render its content can be tricky. These days, more and more sites are using frameworks like Angular, React and Vue.js for their front-end. These front-end frameworks are complicated to deal with because they fire a lot of AJAX calls.

If we had to worry about an asynchronous HTTP call (or many) to an API, there are two ways to solve this:

• Use a time.sleep(ARBITRARY_TIME) before taking the screenshot.
• Use a WebDriverWait object.

If you use a time.sleep() you will probably use an arbitrary value. The problem is, you're either waiting for too long or not enough.Also the website can load slowly on your local wifi internet connection, but will be 10 times faster on your cloud server.With the WebDriverWait method you will wait the exact amount of time necessary for your element/data to be loaded.

This will wait five seconds for an element located by the ID “mySuperId” to be loaded.There are many other interesting expected conditions like:

• element_to_be_clickable
• text_to_be_present_in_element
• element_to_be_clickable

You can find more information about this in the Selenium documentation

Executing Javascript

Sometimes, you may need to execute some Javascript on the page. For example, let's say you want to take a screenshot of some information, but you first need to scroll a bit to see it.You can easily do this with Selenium:

Conclusion

I hope you enjoyed this blog post! You should now have a good understanding of how the Selenium API works in Python. If you want to know more about how to scrape the web with Python don't hesitate to take a look at our general Python web scraping guide.

Selenium is often necessary to extract data from websites using lots of Javascript. The problem is that running lots of Selenium/Headless Chrome instances at scale is hard. This is one of the things we solve with ScrapingBee, our web scraping API

Selenium is also an excellent tool to automate almost anything on the web.

If you perform repetitive tasks like filling forms or checking information behind a login form where the website doesn't have an API, it's maybe* a good idea to automate it with Selenium,just don't forget this xkcd:

Web scraping is a very useful mechanism to either extract data, or automate actions on websites. Normally we would use urllib or requests to do this, but things start to fail when websites use javascript to render the page rather than static HTML. For many websites the information is stored in static HTML files, but for others the information is loaded dynamically through javascript (e.g. from ajax calls). The reason maybe because the information is constantly changing, or it maybe to prevent webscraping! Either way, you need to more advanced techniques to scrape the information – this is where the library selenium can help.

What is web scraping?

To align with terms, web scraping, also known as web harvesting, or web data extraction is data scraping used for data extraction from websites. The web scraping script may access the url directly using HTTP requests or through simulating a web browser. The second approach is exactly how selenium works – it simulates a web browser. The big advantage in simulating the website is that you can have the website fully render – whether it uses javascript or static HTML files.

What is selenium?

According to selenium official web page, it is a suite of tools for automating web browsers. This project is a member of the Software Freedom Conservancy, Selenium has three projects, each provides a different functionality if you are interested in it, visit their official website. The scope of this blog will be attached to the Selenium WebDriver project

When should you use selenium?

Selenium is going to facilitate us with tools to perform web scraping, but when should it be used? You generally can use selenium in the following scenarios:

• When the data is loaded dynamically – for example Twitter. What you see in “view source” is different to what you see on the page (The reason is that “view source” just shows the static HTML files. If you want to see under the covers of a dynamic website, right click and “inspect element” instead)
• When you need to perform an interactive action in order to display the data on screen – a classic example is infinite scrolling. For some websites, you need to scroll to the bottom of the page, and then more entries will show. What happens behind the scene is that when you scroll to the bottom, javascript code will call the server to load more records on screen.

So why not use selenium all the time? It is a bit slower then using requests and urllib. The reason is that selenium simulates running a full browser including the overhead that a brings with it. There are also a few extra steps required to use selenium as you can see below.

Once you have the data extracted, you can still use similar approaches to process the data (e.g. using tools such as BeautifulSoup)

Pre-requisites for using selenium

Web Scraping With Selenium Python

Step 1: Install selenium library

Before starting with a web scraping sample ensure that all requirements have been set, Selenium requires pip or pip3 installed, if you don’t have it installed you can follow the official guide to install it based on the operating system you have.

Once pip is installed you can proceed with the installation of selenium, with the following command

Alternatively, you can download the PyPI source archive (selenium-x.x.x.tar.gz) and install it using setup.py:

Step 2: Install web driver

Selenium simulates an actual browser. It won’t use your chrome installation but it will use a “driver” which is the browser engine to run a browser. Selenium supports multiple web browsers, so you may chose which web browser to use (read on)

Selenium WebDriver refers to both the language bindings and the implementations of the individual browser controlling code. This is commonly referred to as just a web driver.

Web driver needs to be downloaded, and then it could be either added to the path environment variable or initialized with a string containing the path where downloaded web driver is. Environment variables are out of the scope of the blog so we are going to use the second option.

From here to the end Firefox web driver is going to be used, but here is a table containing information regarding each web driver, you are able to choose any of them, Firefox is recommended to follow this blog

Download the driver to a common folder which is accessible. Your script will refer to this driver.

You can follow our guide on how to install the web driver here.

A Simple Selenium Example in Python

Ok, we’re all set. To begin with, let’s start with a quick staring example to ensure things are all working. Our first example will involving collecting a website title. In order to achieve this goal, we are going to use selenium, assuming it is already installed in your environment, just import webdriver from selenium in a python file as it’s shown in the following.

Running the code below will open a firefox window which looks a little bit different as can be seen in the following image and at the then it prints into the console the title of the website, in this case, it is collecting data from ‘Google’. Results should be similar to the following images:

Note that this was run in foreground so that you can see what is happening. Now we are going to manually close the firefox window opened, it was intentionally opened in this way to be able to see that the web driver actually navigates just like a human will do. But now that it is known, we can add at the end of the out this code: driver.quit() so the window will automatically be closed after the job is done. Code now will look like this.

Now the sample will open the Firefox web driver do its jobs and then close the windows. With this little and simple example, we are ready to go dipper and learn with a complex sample

How To Run Selenium in background

In case you are running your environment in console only or through putty or other terminal, you may not have access to the GUI. Also, in an automated environment, you will certainly want to run selenium without the browser popping up – e.g. in silent or headless mode. This is where you can add the following code at the start “options” and “–headless”.

The remaining examples will be run in ‘online’ mode so that you can see what is happening, but you can add the above snippet to help.

Example of Scraping a Dynamic Website in Python With Selenium

Until here, we have figure out how to scrap data from a static website, with a little bit of time, and patience you are now able to collect data from static websites. Let’s now dive a little bit more into the topic and build a script to extract data from a webpage which is dynamically loaded.

Imagine that you were requested to collect a list of YouTube videos regarding “Selenium”. With that information, we know that we are going to gather data from YouTube, that we need the searching result of “Selenium”, but this result will be dynamic and will change all the time.

The first approach is to replicate what we have done with Google, but now with YouTube, so a new file needs to be created yt-scraper.py

Now we are retrieving data YouTube title printed, but we are about to add some magic to the code. Our next step is to edit the search box and fill it with the word that we are looking for “Selenium” by simulating a person typing this into the search. This is done by using the Keys class:

from selenium.webdriver.common.keys import Keys.

The driver.quit() line is going to be commented temporally so we are able to see what we are performing

The Youtube page shows a list of videos from the search as expected!

As you might notice, a new function has been called, named find_element_by_xpath, which could be kind of confusing at the moment as it uses strange xpath text. Let’s learn a little bit about XPath to understand a bit more.

What is XPath?

XPath is an XML path used for navigation through the HTML structure of the page. It is a syntax for finding any element on a web page using XML path expression. XPath can be used for both HTML and XML documents to find the location of any element on a webpage using HTML DOM structure.

The above diagram shows how it can be used to find an element. In the above example we had ‘//input[@id=”search”]. This finds all <input> elements which have an attributed called “id” where the value is “search”. See the image below – under the “inspect element” for the search box from youTube, you can seen there’s a tag <input id=”search” … >. That’s exactly the element we’re searching for with XPath

There are a great variety of ways to find elements within a website, here is the full list which is recommended to read if you want to master the web scraping technique.

Looping Through Elements with Selenium

Now that Xpath has been explained, we are able to the next step, listing videos. Until now we have a code that is able to open https://youtube.com, type in the search box the word “Selenium” and hit Enter key so the search is performed by youtube engine, resulting in a bunch of videos related to Selenium, so let’s now list them.

Selenium For Web Scraping

Firstly, right click and “inspect element” on the video section and find the element which is the start of the video section. You can see in the image below that it’s a <div> tag with “id=’dismissable'”

We want to grab the title, so within the video, find the tag that covers the title. Again, right click on the title and “inspect element” – here you can see the element “id=’video-title'”. Within this tag, you can see the text of the title.

One last thing, let’s remind that we are working with internet and web browsing, so sometimes is needed to wait for the data to be able, in this case, we are going to wait 5 seconds after the search is performed and then retrieve the data we are looking information. Keep in mind that the results could vary due to internet speed, and device performance.

Once the code is executed you are going to see a list printed containing videos collected from YouTube as shown in the following image, which firstly prints the website title, then it tells us how many videos were collected and finally, it lists those videos.

Waiting for 5 seconds works, but then you have to adjust for each internet speed. There’s another mechanism you can use which is to wait for the actual element to be loaded – you can use this a with a try/except block instead.

So instead of the time.sleep(5), you can then replace the code with:

This will wait up to a maximum of 5 seconds for the videos to load, otherwise it’ll timeout

Conclusion

With Selenium you are going to be able to perform endless of tasks, from automation tasks to automate testing, the sky is the limit here, you have learned how to scrape data from static and dynamic websites, performing javascript actions like send some keys like “Enter”. You can also look at BeautifulSoup to extract and search for data next

Subscribe to our newsletter

Get new tips in your inbox automatically. Subscribe to our newsletter!