[Tutor] Interactive editing of variables.

[Steven D'Aprano]

Hi Sean,

On Sat, Jun 01, 2019 at 12:53:00PM +1000, mhysnm1964 at gmail.com wrote:
> I have had a look and cannot find an example where I can interactively edit
> a content of a variable at the command line. I do not want to use GUI at
> all. As this is a simple program only requiring CLI. I have no problems
> showing the prompt, but cannot insert text into the edit (input) area. Any
> ideas?

Let me see if I understand what you are asking for.

The built-in function "input()" takes one argument, the prompt, and lets 
the user type a response. So if I run the function:

    input("What is your name?")

the terminal will display the prompt, and put the text cursor next to 
it. That is how things work now.

I think what you are asking for is the ability to pass a second argument 
to the function, like this:

    input("What is your name?", "George")

and the terminal will display the prompt, then place the word "George" 
next to the prompt in the edit-zone. The user (you) can then backspace 
over the word and type something new, or otherwise edit it.

Is that what you want?

If so, then on Linux or Unix systems, you can do this:


import readline

def myinput(prompt='', initial=''):
    readline.set_startup_hook(lambda: readline.insert_text(initial))
    try:
        response = input(prompt)
    finally:
        readline.set_startup_hook(None)
    return response


The bad news is that this only works on Linux and other Unix systems 
with readline installed (which nearly all of them do). It won't work 
under Windows.

But if you install the third-party library pyreadline, you *may* be able 
to use that instead:

import pyreadline as readline

and the rest might work. (I don't have Windows and can't try it.)


-- 
Steven