How to initialize JS variables through Selenium python?

Question

I am trying to execute a JS file through python, selenium but I think I miss something.

I tried to call the checking variable from safari console, but it shows the following error Can't find the checking variable.

I also tried to execute the following code line driver.execute_script('var checking=0;') but I got the same result when I tried to call the checking variable from Safari Console.

PYTHON CODE

driver.execute_script(open("/Users/Paul/Downloads/pythonProject/Social media/javascripts/Initializing Variables.js").read())

JS FILE

var checking;
function Checking(item) {
    if (item) {
        checking = true;
    }
    else {
        checking = false;
    }
}

Any ideas?

Michael Mintz · Accepted Answer · 2022-01-23 14:50:17Z

3

Here's a quick tutorial on local vs globally scoped variables.

If you run a command such as:

self.execute_script("var xyz = 'abc';")

and then go to the console to try to find xyz, it won't be there (xyz is not defined).

However, if you run:

self.execute_script("document.xyz = 'abc';")

then it will be in the browser console if you type document.xyz.

That's the short summary. If you just try to declare a local variable when run from execute_script, then it'll go out-of-scope after the script is run. However, if you attach a variable to a persistent one, that's one way of keeping the variable around (and still accessible).

edited Jan 23, 2022 at 14:50

answered Jan 23, 2022 at 14:43

Michael Mintz

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4 Comments

Paul Viorel Over a year ago

if you attach a variable to a persistent one What does persistent one mean? I want to store also some functions to call them later from selenium.

Michael Mintz Over a year ago

Attaching a variable to document would make it persistent, so if you define document.myVariable = "ANYTHING; in the script, you'll be able to use it later. If you just define myVariable without the document, then it would go out-of-scope after your script is called and it would not persist.

Paul Viorel Over a year ago

And is there any way to make a whole js file persistent? With a code line or something? Because I also have functions, and document.function X() or function document.X() doesn't work.

Michael Mintz Over a year ago

On the last line of your script file, add: document.Checking = Checking; (That brings over the function. Do a similar action for any variables that you want to carry over - put them in document)

Max Daroshchanka · Accepted Answer · 2022-01-23 16:17:28Z

2

All variables will be available just in single execute_script command context. So it's not possible to define variable in one driver command and modify it or get by another, unless you put the data to document, localstorage or sessionstorage..

But you're able to declare and put something to the variable, just don't forget to return it's value in script.

If I execute this script with driver.execute_script

var a;
function setAValue(arg) {
    a = arg;
}

setAValue(100);
return a;

you'll get 100 in the output result.

And if you want to run your file from script, the file should ends with the function invocation and the return statement.

Share function and variables between scripts

This is working example in groovy language (sorry no python env)

WebDriverManager.chromedriver().setup()
WebDriver driver = new ChromeDriver()

driver.get("https://stackoverflow.com/")
//define variable date and function GetTheDatesOfPosts 
driver.executeScript('''
    document.date = [];
    document.GetTheDatesOfPosts = function (item) { document.date = [item];}
''')

//use them in new script
println (driver.executeScript('''
    document.GetTheDatesOfPosts(7);
    return document.date;
    '''))
driver.quit()

it prints [7].

edited Jan 23, 2022 at 16:17

answered Jan 23, 2022 at 14:42

Max Daroshchanka

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5 Comments

Paul Viorel Over a year ago

Fair enough. so driver.execute_sript is running only local variables & functions. Am I right?

Max Daroshchanka Over a year ago

@PaulViorel it might run global functions too, and access global variables. E.g. access ducument or window. But you not able to define local variable by one script and access it with another script.

Paul Viorel Over a year ago

I declared my variable like that document.date = []; .Function like that document.GetTheDatesOfPosts = function (item) {//code} and when I call this function I get the same error: Can't find variable: date

Max Daroshchanka Over a year ago

@PaulViorel I was able to share the variable and function from your comment without errors, see the updated answer.

Paul Viorel Over a year ago

Thank you, it was my bad... I had a typo, instead of document. I had docmnet..... So frustrating... Thank again

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