I am writing a python/pygtk application that is adding some custom scripts (bash) in a certain folder in $HOME (eg. ~/.custom_scripts). 
I want to make that folder available in $PATH. So every time the python app is adding the script, that script could be instantly available when the user is opening a terminal (eg. gnome-terminal). 
Where do you suggest to "inject" that $PATH dependecy ? .bashrc, /etc/profile.d, etc. ?
What advantages / disadvantages I might encounter ?
For example if i add a script to export the new path in /etc/profile.d, the path is not being updated until I re-login.
Thanks
You shouldn't. It's the user choice whether he wants that in the PATH, in what cases and how to achieve that. What you can do is inform the user about the directory where your scripts reside and suggest putting it to the PATH.
Or maybe you're asking from the user's perspective?
How to update $PATH