I have a folder called raw_files. Very large files (~100GB files) from several sources will be uploaded to this folder. 
I need to get file information from videos that have finished uploading to the folder. What is the best way to determine if a file is currently being downloaded to the folder (pass) or if the video has finished download (run script)? Thank you.
If you check those files, store the size of the files somewhere. When you are in the next round and the filesize is still the same, you can pretty much consider them as finished (depending on how much time is between first and second check). The time interval could e.g. be set to the timeout-interval of your uploading service(FTP, whatever).
There is no special sign or content showing that a file is complete.
How to determing if a file has finished downloading in python