Baffled by readline module

[Cameron Simpson]

On 10Mar2023 23:11, Weatherby,Gerard <gweatherby at uchc.edu> wrote:
>This is the implementation of cmd.Cmd (Python 3.9). As you can see in cmdloop(), the import is already wrapped, and the readline feature can be turned off explicitly by passing None to the completekey in the constructor.

This isn't strictly true, as I read it.

This says that if you supply a `completekey`, _then_ `cmdloop` will try 
to import `readline` and set up working completion for that key.

It _doesn't_ say that readline is or is not automatically active for its 
other features (command line editing, history etc).

Having a gander further down the `cmdloop` function we see:

     while not stop:
         if self.cmdqueue:
             line = self.cmdqueue.pop(0)
         else:
             if self.use_rawinput:
                 try:
                     line = input(self.prompt)
                 except EOFError:
                     line = 'EOF'

and on a Python 3.10 here we see:

     >>> help(input)
     Help on built-in function input in module builtins:

     input(prompt=None, /)
         Read a string from standard input.  The trailing newline is stripped.

         The prompt string, if given, is printed to standard output without a
         trailing newline before reading input.

         If the user hits EOF (*nix: Ctrl-D, Windows: Ctrl-Z+Return), raise EOFError.
         On *nix systems, readline is used if available.

which says to me that readline is used if available, regardless of 
whether it is already imported.

Cheers,
Cameron Simpson <cs at cskk.id.au>