Delete all contents of a file from the fifth line?

[PythonNPC]

Hello,

I want to delete all the contents of the file from under the fifth line.

Is this doable?
I don't want to just print the file on the console, I actually want the contents of the file to be deleted from the fifth line and then to be saved.

I tried searching on the internet but was not able to find anything, maybe I just suck search at searching.

Can anyone help?
Thank you.