How to place a default file name in the file dialog asksaveasfile python

Question

I would like to place a value in the file dialog by default when the user is saving a file. Anyone can advise the syntax of it ?

saveFilePath = fileDialog.asksaveasfile(mode='w', title="Save the file", defaultextension=".txt")

For example: NewFile should be filled in when the file dialog is open

Answer 1

initialfile

as proposed by Bryan Oakley worked.