make a Client-Server application
The "action" part of a form is an url, and If you don't specify the scheme://host:port part of the URL, the client will resolve it has the current page one. IOW: just put the path part of your script's URL and you'll be fine. FWIW hardcoding the scheme://host:port of your URLs is an antipattern, as you just found out.
I used to create web app in the same computer, but if the server and the client is not in the same computer, how can we access to the web page ?
I mean, for example I have an html form and a button "ok" :
If the server and the client are in the same computer, in action = " " we put localhost/file.py , but if the server and the client are not in the same computer how to do this ? Because the client can't to have localhost in his webbrower (url).