(embedding) running Python as coprocess

Jp Calderone exarkun at intarweb.us
Wed Feb 19 23:01:23 CET 2003

On Wed, Feb 19, 2003 at 09:40:09PM +0000, William Park wrote:
> I've managed to fully embed Python into Bash.  But, the result is 1.4Meg
> in size.  I'm wondering if there is better and more general way of
> running Python as coprocess in the background.
> That is, with Python running in the background, I want to send one batch
> of commands to Python and read the result back, send another batch and
> read the result, and so on.  Python should not terminate between
> batches, because I want to access data from previous calls.
> I've tried something like
>     python <fifo.in >fifo.out &
>     echo "print 2.0+3.0" > fifo.in
>     cat fifo.out
> I get the result, but Python terminates as soon as EOF is reached in the
> <stdin> stream.
> My embedded Python will stay alive between batches.  But, this solves
> problem only for Python.  Any insight to solving this problem for a any
> external program (ie. Perl, Ruby, etc.) would be greatly appreciated.

  Instead of running -just- Python, run a Python program.  It can attach
itself to a couple fifos (or a unix socket, or a tcp socket, or ...), read
until EOF, process the string (easy, with exec/eval), write the results out,
then re-open the input file.

  There's also a project that keeps a Python interpreter running and lets
you use a mini-interpreter (for the #!) to connect to it, but I forget the
name.  It was mentioned on this group a week or two ago, so maybe you can
find it w/ a little searching.


It is practically impossible to teach good programming style to
students that have had prior exposure to BASIC: as potential
programmers they are mentally mutilated beyond hope of
regeneration.        -- Dijkstra
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