how to handle multi line in test complete python script

You want to use Keys to write multiple lines? Then you need to have the carriage return key '\r' or line break '\n' on each line.

For example,

var str1 = "Hello\rWorld";
var str2 = "Hello\nWorld";
var str3 = "Hello\r\nWorld";

// Which will print

Hello

World

See https://stackoverflow.com/questions/7630273/convert-multiline-into-list. Store each line into an array.

I was not aware that those were array values, as you did not mention it. However, you will need to construct a string like so,

function test10()
{
    var L = [1, 2, 3];
    var U2 = ["A", "B", "C"];

    var str =
        "S2F33_DefineReport_Job: 'S2F33' W" +
        "<" + L[2] +
        "<" + U2[1] + "1> /* DATAID */";
        
    Log.Message(str); // Output string to see if format is correct
}

See https://stackoverflow.com/questions/7975005/format-a-javascript-string-using-placeholders-and-an-object-of-substitutions for substitutions values.

So you don't want to use Keys to write muliple lines?

Would it be possible to explain exactly what you are trying to do, so that I can understand better, and provide a solution?

Here's script code to enter mutlple lines in a text area,

function testarea()
{
    // https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_textarea
    var browser = Sys.Browser("chrome");
    var page = browser.Page("https://www.w3schools.com/tags/tryit.asp?filename=tryhtml_textarea");
    var textarea = page.Panel("container").Panel("iframecontainer").Panel("iframe").Panel("iframewrapper").Frame("iframeResult").Form(0).Textarea("w3review");
    textarea.Keys("~a[Del]");
    textarea.Keys("S2F33_DefineReport_Job: 'S2F33' W\r<L[2]\r<U2[1] 1> /* DATAID */\r<L[1]\r<L[2]\r<U4[1] 8010> /* RPTID */\r<L[2]\r<U4[1] 8010> /* Clock */\r>\r>\r>\r>.");
}

Which is in the same format.