On my system exactly the same code as above also opens the script for editing....

BUT

this is not a robust solution - it only works for me because in my OS I have chosen to open Python script files by default with TextEdit.

EDIT: cross-post.. I'll try the update.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)