Headless Browser in Python
A headless browser can access any website but unlike normal browsers (which you currently use) nothing will appear on the screen. Everything is done on the backend side invisible to the user.
What is headless testing?
Executing the web applications UI tests without opening a browsers user interface is called headless browser testing. A Headless browser will similarly act like a normal web browser. Testers will have full control over the web pages loaded into the headless browsers the only difference is you will not see a graphical user interface.
Why do we need headless browser?
Headless browser automation uses a web browser for end-to-end tests but skips loading the browsers’ UI. … headless browser automation may make it possible for you to add end-to-end tests to your testing process.
What do we want to do?
**Assuming that “Python is installed and IDE(ex.PyCharm) is ready to write the test script in python file”.
Let’s launch Chrome with and without headless mode , hit the indeed website , maximize the screen , send keys “selenium” in the search field and record the time required for this task.
Getting Started with Headless Chrome :
First, let’s import everything we’ll need to run Chrome in headless mode using Selenium.
Defining Chrome
Before we set up a Chrome webdriver instance, we have to create an Options object that allows us to specify how exactly we want to launch Chrome. Let’s tell it that we want the browser to launch headless and that the window size should be set to 1920×1080
Launching Chrome
Now that we have everything we need, we can jump into action! Create an instance of Chrome webdriver and pass it the the Options object we created earlier and the path to the actual ChromeDriver tool. Using the driver, go to the indeed.com, maximize the window and send keys Selenium. Don’t forget to set timer to log the time.
After executing this we get the result in console as :
Getting Started without Headless Chrome :
We will be following the same steps except we will define the chrome browser without headless argument .
Defining and launching Chrome:
1. First import the webdriver and Keys classes from Selenium.
2. Next, create an instance of Chrome with the path of the driver.
3. Using the driver, go to the indeed.com, maximize the window and send keys Selenium. Don’t forget to set timer to log the time.
After executing this we get the result in console as :
Conclusion :
The recorded time for script execution with headless browser is 3.3800173 seconds and without headless browser is 4.6863921 seconds . so we can conclude it in terms of speed and data extraction .
- Speed: Since headless browsers don’t have a UI, they are faster than real browsers .
- Data Extraction : If your task is to scrape some data from website headless browser would do it much faster.
To rapidly test the application in various browsers and without any interruption, headless browser testing is used.
**If you are about to start your journey with headless Selenium, I recommend to use Chrome or Firefox. You can easily debug any issues by commenting — headless switch and see actual browser behavior.
python browser
Python browser with PyQt4
In this tutorial we will build a webbrowser with Python. We will use the PyQT library which has a web component. In this tutorial you will learn how to link all the components together. We will use the default rendering engine and not roll one in this tutorial.
If you have not done our pyqt4 beginner tutorial, you could try it. If python-kde4 cannot be found update your repository to find it. The Ubuntu or Debian install guide .
Related course:
PyQt installation
Creating the GUI with PyQT
QT_Designer
Select Main Window and press Create. We now have our designer window open. Drag a KWebView component on the window. If you have a QtWebView (qtwebkit) in the component list. use that instead. We also add an Line Edit on top. Press File > Save As > browser.ui. Run the command:
This will generate a Python file. Remove the line “from kwebview import KWebView” from the bottom of the browser.py file. Change KWebView to QtWebView. We want to use QtWebView instead. If you are lazy to change that, take the browser.py file from below.
QWebView exploration
This code will use the UI as defined in browser.py and add logic to it. The lines
The first line defines the callback or event. If a person presses enter (returnPressed), it will call the function loadURL. It makes sure that once you press enter, the page is loaded with that function. If you did everything correctly, you should be able to run the browser with the command:
Please make sure you type the full url, e.g. : https://pythonspot.com including the http:// part. Your browser should now start:
<caption align=”alignnone” width=”1026”] Python browser
If your code does not run, please use the codes below (or look at the differences and change whats wrong):
webbrowser — Convenient web-browser controller¶
The webbrowser module provides a high-level interface to allow displaying web-based documents to users. Under most circumstances, simply calling the open() function from this module will do the right thing.
Under Unix, graphical browsers are preferred under X11, but text-mode browsers will be used if graphical browsers are not available or an X11 display isn’t available. If text-mode browsers are used, the calling process will block until the user exits the browser.
If the environment variable BROWSER exists, it is interpreted as the os.pathsep -separated list of browsers to try ahead of the platform defaults. When the value of a list part contains the string %s , then it is interpreted as a literal browser command line to be used with the argument URL substituted for %s ; if the part does not contain %s , it is simply interpreted as the name of the browser to launch. 1
For non-Unix platforms, or when a remote browser is available on Unix, the controlling process will not wait for the user to finish with the browser, but allow the remote browser to maintain its own windows on the display. If remote browsers are not available on Unix, the controlling process will launch a new browser and wait.
The script webbrowser can be used as a command-line interface for the module. It accepts a URL as the argument. It accepts the following optional parameters: -n opens the URL in a new browser window, if possible; -t opens the URL in a new browser page (“tab”). The options are, naturally, mutually exclusive. Usage example:
Availability : not Emscripten, not WASI.
This module does not work or is not available on WebAssembly platforms wasm32-emscripten and wasm32-wasi . See WebAssembly platforms for more information.
The following exception is defined:
exception webbrowser. Error ¶
Exception raised when a browser control error occurs.
The following functions are defined:
webbrowser. open ( url , new = 0 , autoraise = True ) ¶
Display url using the default browser. If new is 0, the url is opened in the same browser window if possible. If new is 1, a new browser window is opened if possible. If new is 2, a new browser page (“tab”) is opened if possible. If autoraise is True , the window is raised if possible (note that under many window managers this will occur regardless of the setting of this variable).
Note that on some platforms, trying to open a filename using this function, may work and start the operating system’s associated program. However, this is neither supported nor portable.
Raises an auditing event webbrowser.open with argument url .
webbrowser. open_new ( url ) ¶
Open url in a new window of the default browser, if possible, otherwise, open url in the only browser window.
webbrowser. open_new_tab ( url ) ¶
Open url in a new page (“tab”) of the default browser, if possible, otherwise equivalent to open_new() .
webbrowser. get ( using = None ) ¶
Return a controller object for the browser type using. If using is None , return a controller for a default browser appropriate to the caller’s environment.
webbrowser. register ( name , constructor , instance = None , * , preferred = False ) ¶
Register the browser type name. Once a browser type is registered, the get() function can return a controller for that browser type. If instance is not provided, or is None , constructor will be called without parameters to create an instance when needed. If instance is provided, constructor will never be called, and may be None .
Setting preferred to True makes this browser a preferred result for a get() call with no argument. Otherwise, this entry point is only useful if you plan to either set the BROWSER variable or call get() with a nonempty argument matching the name of a handler you declare.
Changed in version 3.7: preferred keyword-only parameter was added.
A number of browser types are predefined. This table gives the type names that may be passed to the get() function and the corresponding instantiations for the controller classes, all defined in this module.
How to Create Webkit Browser with Python
In this tutorial we’ll create simple web browser using Python PyQt framework. As you may know PyQt is a set of Python bindings for Qt framework, and Qt (pronounced cute) is C++ framework used to create GUI-s. To be strict you can use Qt to develop programs without GUI too, but developing user interfaces is probably most common thing people do with this framework. Main benefit of Qt is that it allows you to create GUI-s that are cross platform, your apps can run on various devices using native capabilities of each platform without changing your codebase.
Qt comes with a port of webkit, which means that you can create webkit-based browser in PyQt.
Our browser will do following things:
- load urls entered by user into input box
- show all requests performed while rendering the page
- allow you to execute custom JavaScript in page context
Hello Webkit
Let’s start with simplest possible use case of PyQt Webkit: loading some url, opening window and rendering page in this window.
This is trivial to do, and requires around 13 lines of code (with imports and whitespace):
If you pass url to script from command line it should load this url and show rendered page in window.
At this point you maybe have something looking like command line browser, which is already better than python-requests or even Lynx because it renders JavaScript. But it’s not much better than Lynx because you can only pass urls from command line when you invoke it. We definitely need some way of passing urls to load to our browser.
Add address bar
To do this we’ll just add input box at the top of the window, user will type url into text box, browser will load this url. We will use QLineEdit widget for input box. Since we will have two elements (text input and browser frame), we’ll need to add some grid layout to our app.
At this point you have bare-bones browser that shows some resembrance to Google Chrome and it uses same rendering engine. You can enter url into input box and your app will load url into browser frame and render all HTML and JavaScript.
Add dev tools
Of course the most interesting and important part of every browser are its dev tools. Every browser worth its name should have its developer console. Our Python browser should have some developer tools too.
Let’s add something similar to Chrome “network” tab in dev tools. We will simply keep track of all requests performed by browser engine while rendering page. Requests will be shown in table below main browser frame, for simplicity we will only log url, status code and content type of responses.
Do do this we will need to create a table first, we’ll use QTableWidget for that, header will contain field names, it will auto-resize each time new row is added to table.
To keep track of all requests we’ll need to get bit deeper into PyQt internals. Turns out that Qt exposes NetworkAccessManager class as an API allowing you to perform and monitor requests performed by application. We will need to subclass NetworkAccessManager, add event listeners we need, and tell our webkit view to use this manager to perform its requests.
First let’s create our network access manager:
I have to say that some things in Qt are not as easy and quick as they should be. Note how awkward it is to get status code from response. You have to use response method .attribute() and pass reference to class property of request. This returns QVariant not int and when you convert to int it returns tuple.
Now finally we have a table and a network access manager. We just need to wire all this together.
Now fire up your browser, enter url into input box and enjoy the view of all requests filling up table below webframe.
If you have some spare time you could add lots of new functionality here:
- add filters by content-type
- add sorting to table
- add timings
- highlight requests with errors (e.g. show them in red)
- show more info about each request — all headers, response content, method
- add option to replay requests and load them into browser frame, e.g. user clicks on request in table and this url is loaded into browser.
This is long TODO list and it would be probably interesting learning exercise to do all these things, but describing all of them would probably require to write quite a long book.
Add way to evaluate custom JavaScript
Finally let’s add one last feature to our experimental browser — ability to execute custom JavaScipt in page context.
After everything we’ve done earlier this one comes rather easily, we just add another QLineEdit widget, connect it to web page object, and call evaluateJavaScript method of page frame.
then we instantiate it in our main clause and voila our dev tools are ready.
Now the only thing missing is ability to execute Python in page context. You could probably develop your browser and add support for Python along JavaScript so that devs writing apps targeting your browser could.
Moving back and forth, other page actions
Since we already connected our browser to QWebPage object we can also add other actions important for end users. Qt web page object supports lots of different actions and you can add them all to your app.
For now let’s just add support for “back”, “forward” and “reload”. You could add those actions to our GUI by adding buttons, but it will be easier to just add another text input box.
just as before you also need to create instance of ActionInputBox, pass reference to page object and add it to our GUI grid.