Calling external program from within python

[oj]

On Jul 25, 3:44 pm, "Diez B. Roggisch" <de... at nospam.web.de> wrote:
> Because usually if a program *prompts* the user to enter input (and that
> was what I read from the OP's post), one has to deal with pseudo
> terminals, not with stdin/out.

How does the program writing some text before taking input change how
it takes input?

If it runs in a terminal and takes input from the user via keyboard,
as in the user types a response and presses enter, it's most likely
using stdin, in which case subprocess would be perfect.

Perhaps that OP can clarify how the tcal program takes input?