I have found a way to do it not externally.
I post this in hope that it will help someone else struggling to find out how to do it within the software itself (Adobe Animate).
Here's a snippest of the code doing that (that is not optimized).
By the way it is really inspired by an answer on StackOverFlow (I do not remember the link).
var swfFolder = 'Path/to/SWF/Files'
var flaFolder = fl.browseForFolderURL('Path/to/FLA/Files');
var folderContents = FLfile.listFolder(flaFolder);
for(i = 0; i < folderContents.length; i++){
file = folderContents[i];
swfFilename = file.replace(".fla", ".swf");
file = 'Path/to/FLA/Files' + file;
fl.openDocument(file);
fl.getDocumentDOM().exportSWF(swfFolder + "/" + swfFilename, true);
fl.closeDocument(file);
}
It has some problems. The first time you execute this script, it will open a sort of browser file in order to choose the directory in which FLA files are located. and then pressing on ok
for each file.
But if you want just a script that does the export on a one file only, the code above will be helpfull:
var swfFolder = 'Path/to/SWF/Files';
var swfFilename = "exportedFile.swf";
fl.getDocumentDOM().exportSWF(swfFolder + "/" + swfFilename, true);
In order to answer fully to my question (executing externally a code that exports FLA files to SWF files), we have to found out how to execute this script from a command line (cmd in Windows). Then to extend it to a folder of many files.fla, we can make a little Python code that calls the script on each file of the FLA directory.
However, I didn't find how to achieve that. So if someone has the answer to that, please let us know.
EDIT
To call a JSFL script on a FLA file, use:
Path\To\Animate.exe file.fla Path\To\file.jsfl
(Link to the reference)
When I had to make a Python script for that purpose, this whole command didn't work for me, I had to first open Adobe Animate
with my fla file, wait some seconds (using time.sleep()) and then call the command
Path\To\Animate.exe Path\To\file.jsfl