[Tutor] TCL fileevent --> Python ???

[Evgeny Roubinchtein]

I am teaching myself Tkinter by rewriting the examples in "Practical
Programming in TCL and Tk" in Python.  They have a sample application
which runs a command and captures and displays the commands output in a
Text widget.  The user types the command in an Entry widget, clicks the
"Run" button and then "it cooks".  I am stuck on translating the "Run"
button's callback; the TCL code is:

proc Run {} {
    global command input log btnRun
    # command -- is the text user typed in the Entry widget
    # log -- is the Text widget in which the command's output is captured
    # btnRun -- is the "Run" button
    if [catch {open "| $command |& cat"} input] {
        # some kind of error happened
        $log insert end $input\n
    } else {
        # opened the pipe OK
        fileevent $input readable Log # call Log whenever something
                                      # comes in from the pipe
                                      # how do you say something similar
                                      # in Python?
        $log insert end $command\n
        $btnRun config -text Stop -command Stop
    }
}

Well, I am sort of stumped on translating "fileevent": looking at its
man page, it behaves just like the TK/Tkinter's "bind" method, except
that "bind" calls a procedure when there's an X event, and "filevent"
calls procedure when some input is waiting to be read, so the read
won't 'block', so the application doesn't look "frozen" to the user.

Looking through Python library I didn't find anything I could use "out
of the box", I think if I started a new thread (or used fork) I could
have one process/thread handling the input from the pipe and the other
handling the button clicks -- I will play with that idea but if this
sounds like something someone has done before, I would love to hear
from them.

Thank you

--
Evgeny Roubinchtein, eroubinc@u.washington.edu
...................
..... REALITY.SYS Corrupted - Unable to recover Universe