Python and multiple user access via super cool fancy website

[Jason Friedman]

> I am not sure if this is the correct venue for my question, but I'd like to
> submit my question just in case.  I am not a programmer but I do have an
> incredible interest in it, so please excuse my lack of understanding if my
> question isn't very thorough.
>
> As an example, a website backend is developed using Python.  Users can
> submit their input through the website and PHP (or some other language)
> transfers the user input from the website fields to a database such as
> MySQL.  There is a main script called main_script.py which extracts the
> user data from MySQL, processes it, stores output in MySQL and sends output
> to the user (via webpage and email).
>
> About main_script.py
> # main_script.py extracts user input from MySQL, processes it, stores
> output in MySQL and send output to user (via webpage and email).
> # Inputs: User personal information such as age, dob, nationality, hobbies,
> and 20 or 30 other fields
> # Output: main_script.py is going to do something with it such as access
> the database and some shelve files or other py scripts. I have no clue what
> it's going to do, but my point is that the processing of the input to
> output will take longer than simply a print('Hello, %r!' %user_name).
>
> My question:  I am curious to know how Python handles something like this.
> Let's say that there are 10, 20, 50, or even 1000 users accessing the
> website.  They all put in their 20 to 30 pieces of input and are waiting on
> some fancy magic output.  How exactly does that work?  Can multiple users
> access the same script?  Does the Python programmer need to code in a
> manner that supports this?  Are requests to the script handled serially or
> in parallel?

I have a hunch that you do not want to write the program, nor do you
want to see exactly how a programmer would write it?

The question is more like asking a heart surgeon how she performs
heart surgery:  you don't plan to do it yourself, but you want a
general idea of how it is done?  How do you keep the patient from
bleeding to death?  Does the heart stop while performing the surgery,
and if yes, how does the patient stay alive?