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[on topic] Re: readline trick needed

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Steven D'Aprano wrote:

> I'm working with the readline module, and I'm trying to set a key
> combination to process the current command line by calling a known
> function, *and* enter the command line.
> 
> Something along the lines of:
> 
> * execute function spam() in some context where it can access
>   the current command line as a string
> * enter the command line
> 
> Function spam() may or may not modify the command line.

> (P.S. I'm aware of IPython, I want to get this working in the standard
> CPython interpreter.)

If IPython does what you want why don't you have a look at the source?

Anyway, here's what I came up with (no warranties as it was all trial-and-
error):

$ cat readline_callback.py
import ctypes
import ctypes.util
from ctypes import c_int, c_char_p
import readline
import sys

rlname = ctypes.util.find_library("readline")

# int rl_add_defun (const char *name, rl_command_func_t *function, int key)
# typedef int rl_command_func_t (int, int);
# int rl_done
# char * rl_line_buffer

rl = ctypes.CDLL(rlname)

RL_COMMAND_FUNC = ctypes.CFUNCTYPE(c_int, c_int, c_int)

intercepted_line = None
def lovely_spam(a, b):
    global intercepted_line
    print
    intercepted_line = c_char_p.in_dll(rl, "rl_line_buffer").value
    rl.rl_insert_text("*" + intercepted_line)
    c_int.in_dll(rl, "rl_done").value = 1
    return 0

def control(c):
    return ord(c.upper())-64

rl.rl_add_defun("lovely-spam", RL_COMMAND_FUNC(lovely_spam), control("P"))

#rl.rl_add_defun("lovely-spam", RL_COMMAND_FUNC(lovely_spam), -1)
#readline.parse_and_bind("Control-P: lovely-spam")

$ python -i readline_callback.py 
>>> alpha = 42
>>> alpha
1764

The relevant documentation:
http://cnswww.cns.cwru.edu/php/chet/readline/readline.html
http://docs.python.org/library/ctypes.html

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readline trick needed Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-13 13:30 +0000
  Re: readline trick needed Etienne Robillard <animelovin@gmail.com> - 2012-10-13 09:44 -0400
  Re: readline trick needed Chris Angelico <rosuav@gmail.com> - 2012-10-14 00:47 +1100
  Re: readline trick needed Etienne Robillard <animelovin@gmail.com> - 2012-10-13 09:58 -0400
  Re: readline trick needed Roel Schroeven <roel@roelschroeven.net> - 2012-10-13 23:14 +0200
  Re: readline trick needed Chris Angelico <rosuav@gmail.com> - 2012-10-14 08:44 +1100
  Re: readline trick needed Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-10-13 23:13 +0100
  Re: readline trick needed Chris Angelico <rosuav@gmail.com> - 2012-10-14 09:41 +1100
  Re: readline trick needed Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-10-13 23:52 +0100
  Re: readline trick needed Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-10-14 01:32 +0100
  [on topic] Re: readline trick needed Peter Otten <__peter__@web.de> - 2012-10-16 10:30 +0200
    Re: [on topic] Re: readline trick needed Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-16 11:27 +0000
      Re: [on topic] Re: readline trick needed Robert Kern <robert.kern@gmail.com> - 2012-10-16 13:20 +0100
        Re: [on topic] Re: readline trick needed Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-16 12:52 +0000
      Re: [on topic] Re: readline trick needed Dwight Hutto <dwightdhutto@gmail.com> - 2012-10-16 10:14 -0400
      [off topic], was Re: [on topic] Re: readline trick needed Peter Otten <__peter__@web.de> - 2012-10-16 16:36 +0200
      Re: [off topic], was Re: [on topic] Re: readline trick needed Dwight Hutto <dwightdhutto@gmail.com> - 2012-10-16 11:14 -0400
  Re: [on topic] Re: readline trick needed Ned Deily <nad@acm.org> - 2012-10-16 01:50 -0700
  Re: [on topic] Re: readline trick needed Peter Otten <__peter__@web.de> - 2012-10-16 12:20 +0200
  Re: [on topic] Re: readline trick needed Ned Deily <nad@acm.org> - 2012-10-16 13:44 -0700

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