readline trick needed

[Steven D'Aprano]

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.

Here is what I have got so far: I can discard the current line and call a
function:

readline.parse_and_bind(r'"\C-p": "%cspam()\n"' % 0x15) # ^U

binds ctrl-P to the key combinations `ctrl-U spam() Enter`, which clears
the command line before entering spam().

If I leave out the ctrl-U, I'll get a SyntaxError or other exception,
e.g. command line `x = 123` gets transformed into `x = 123spam()`.


This is not suitable:

readline.parse_and_bind(r'"\C-p": "; spam()\n"')

because it changes the command line. It's okay for spam() itself to
modify the command line, but the key binding should not.

I tried to do this:

readline.parse_and_bind(r'"\C-p": "\nspam()\n"')

but it gives me a segmentation fault, which is a little less helpful than
I had expected.

This Stackoverflow question suggests that what I want is not possible in
vanilla Python:

http://stackoverflow.com/questions/11680356


but I'm a stubborn guy and I have not given up yet. Any suggestions?


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

 

[Etienne Robillard]

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.

Here is what I have got so far: I can discard the current line and call a
function:

readline.parse_and_bind(r'"\C-p": "%cspam()\n"' % 0x15) # ^U

binds ctrl-P to the key combinations `ctrl-U spam() Enter`, which clears
the command line before entering spam().

If I leave out the ctrl-U, I'll get a SyntaxError or other exception,
e.g. command line `x = 123` gets transformed into `x = 123spam()`.


This is not suitable:

readline.parse_and_bind(r'"\C-p": "; spam()\n"')

because it changes the command line. It's okay for spam() itself to
modify the command line, but the key binding should not.

I tried to do this:

readline.parse_and_bind(r'"\C-p": "\nspam()\n"')

but it gives me a segmentation fault, which is a little less helpful than
I had expected.

This Stackoverflow question suggests that what I want is not possible in
vanilla Python:

http://stackoverflow.com/questions/11680356


but I'm a stubborn guy and I have not given up yet. Any suggestions?


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

Why dont you grow yourself some usable neurons instead ? Don't you realize now stackoverflow.com is starting
to hurt your capacity to cogitate on your own or have you not realized this yet?

Cheers,

Etienne


--
Etienne Robillard
Green Tea Hackers Club
Fine Software Carpentry For The Rest Of Us!
http://gthc.org/
(e-mail address removed)

 

[Chris Angelico]

Why dont you grow yourself some usable neurons instead ? Don't you realize now stackoverflow.com is starting
to hurt your capacity to cogitate on your own or have you not realized this yet?

Excuse me?

I'm not overly familiar with readline, so perhaps there is a really
obvious way to do what Steven's trying to do, but this post does not
appear to be the result of a lack of thinking.

If it really IS that obvious to you, post a link to appropriate
documentation without the rudeness... that way it'll be useful to
everyone, not just cathartic to you.

ChrisA

 

[Etienne Robillard]

Excuse me?

I'm not overly familiar with readline, so perhaps there is a really
obvious way to do what Steven's trying to do, but this post does not
appear to be the result of a lack of thinking.

If it really IS that obvious to you, post a link to appropriate
documentation without the rudeness... that way it'll be useful to
everyone, not just cathartic to you.

ChrisA

whatever. i don't feel much like replying to idiots today so your apologies
and useless if not irrelevant.



--
Etienne Robillard
Green Tea Hackers Club
Fine Software Carpentry For The Rest Of Us!
http://gthc.org/
(e-mail address removed)

 

[Roel Schroeven]

Etienne Robillard schreef:

whatever. i don't feel much like replying to idiots today

Then simply don't. Much better then replying in such a rude way.

I leave the question of who is being an idiot here as an exercise to the
reader.

--
"Too often we hold fast to the cliches of our forebears. We subject all
facts to a prefabricated set of interpretations. Too often we enjoy the
comfort of opinion without the discomfort of thought."
-- John F Kennedy

(e-mail address removed)

 

[Chris Angelico]

With two irritants (including 88888), is it not advisable that python-list
gets an admin to block these accounts? Even if it does nothing more than
slow them, that's something.

That's what killfiles are for. You have two options:

http://en.wikipedia.org/wiki/Kill_file
http://bofh.ch/bofh/bsmh2.html

The first option is not perfect, as you'll still see replies that
quote such people's posts. The second has a few issues with local law
enforcement, but other than that, is a very effective means of
avoiding seeing their posts.

ChrisA

 

[Mark Lawrence]

With two irritants (including 88888), is it not advisable that python-list
gets an admin to block these accounts? Even if it does nothing more than
slow them, that's something.

Most irritants are mere amateurs compared to Ilias Lazaridis. I wonder
if he's *STILL* researching?

 

[Chris Angelico]

The first's no good for protecting the newbies though. If troll flames
newbie, then I want to be able to assure newbie that he's not done anything
wrong or stupid.

The second is a bit better, definitely, but what I'm wanting is to delegate
these tasks to python-list's admins. I'm lazy, see.

Agreed, defending newbies is important. But not everyone gets
frustrated at trolls. Those who don't, don't bother to killfile them,
and can respond in defense of the newbies. Also, if two or three
non-trolls respond to the original post, the angry troll is only one
of several, which helps dilute the problem a bit. Still not a
solution, but it helps.

ChrisA

 

[Mark Lawrence]

My god, he even has an encyclopaedia
entry<http://www.nationmaster.com/encyclopedia/Ilias-Lazaridis>.
Is he some kind of deity?

Oh no he's far higher up the food chain than that. Here's a starter
https://groups.google.com/forum/?fr...anned/comp.lang.ruby/plR34TbM3vc/Ev-Hj5F8oKcJ

 

[Mark Lawrence]

Oh no he's far higher up the food chain than that. Here's a starter
https://groups.google.com/forum/?fr...anned/comp.lang.ruby/plR34TbM3vc/Ev-Hj5F8oKcJ

Yes a real pro. Trolling will never become an Olympic sport as the
guy's so good nobody can compete with him. (If he was American they'd
still have a World Series though Throw his name plus Eclipse,
Netbeans and banned into your search engine of choice and enjoy, but
beware that to really endulge yourself please stock up on vast
quantities of caffeine and sandwiches first cos you'll need them. For
example this http://web.archiveorange.com/archive/v/7IfPlywrYZb0gAgMsPa1
points to this http://www.tfeb.org/lisp/mad-people.html

 

[Peter Otten]

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.py1764

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

 

[Ned Deily]

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.

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

Keep in mind that the Python readline module may be linked to either the
GPL-licensed GNU readline or the BSD-licensed editline (libedit) library
(the default on newer OS X systems and probably on *BSD systems) and
they have different command strings. Note the warning here:

http://docs.python.org/py3k/library/readline.html

Or it may not be linked with either.

 

[Peter Otten]

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.

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

[...]

Keep in mind that the Python readline module may be linked to either the
GPL-licensed GNU readline or the BSD-licensed editline (libedit) library
(the default on newer OS X systems and probably on *BSD systems) and
they have different command strings. Note the warning here:

http://docs.python.org/py3k/library/readline.html[/QUOTE]

I think you are a Mac user. If so, can the snippet I posted be generalised
to work with libedit?

Or it may not be linked with either.

OK, change "no warranties" to "absolutely no warranties"

 

[Steven D'Aprano]

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

Well, I was hoping for a pure Python solution, rather than having to
troll through who knows how many thousands of lines of code in a language
I can barely read.

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

$ cat readline_callback.py
import ctypes

Ah, ctypes.

Well, I guess I have some interesting study ahead of me, to make head or
tail of your solution. Thank you!

 

[Robert Kern]

Well, I was hoping for a pure Python solution, rather than having to
troll through who knows how many thousands of lines of code in a language
I can barely read.

Are you confusing IPython, the pure Python REPL for CPython, for IronPython, the
C# implementation of Python?

https://github.com/ipython/ipython

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco

 

[Steven D'Aprano]

On 10/16/12 12:27 PM, Steven D'Aprano wrote:

Are you confusing IPython, the pure Python REPL for CPython,

IPython is pure Python?

Well, you learn something new everyday. Or at least I do.

I guess that means that I can look forward to trolling through 250 or so
Python modules instead of C code


Thanks to everyone who replied.

 

[Dwight Hutto]

I'm working on the dictionary now,but I came up with this, which uses
a list as the key, and accepts the params to perform the function:

import subprocess as sub
key_list = ['print_something','espeak']

def print_something(params):
print "%s" % (params)

def espeak(params):
sub.call(['espeak','%s' % (params)])

key = raw_input("Please enter key: ")

for line in key_list:
if str(line) == key:
params = raw_input("Enter Params: ")
eval("%s('%s')" % (key,params))


I keep getting the function performed in the dict. I'll figure it out
eventually, I know I've done it before, and it might be a lambda
solution...not sure.

But the above could be refined more, it just uses a list, and key/params.

 

[Peter Otten]

Dwight Hutto wrote:

I knew I'd eventually regret putting "on topic" into the subject...

Well done, Dwight.

 

[Dwight Hutto]

Dwight Hutto wrote:

I knew I'd eventually regret putting "on topic" into the subject...

I didn't write that. If you're referring to OT, it means Off Topic,
and a response would be appreciated. And you can call me David, I go
by my middle name.

 

[Ned Deily]

Keep in mind that the Python readline module may be linked to either the
GPL-licensed GNU readline or the BSD-licensed editline (libedit) library
(the default on newer OS X systems and probably on *BSD systems) and
they have different command strings. Note the warning here:

http://docs.python.org/py3k/library/readline.html

I think you are a Mac user. If so, can the snippet I posted be generalised
to work with libedit?[/QUOTE]

Isn't it hairy enough??

Here's how to make tab complete work with both; it gives an idea of the
libedit commands:

import rlcompleter
if 'libedit' in readline.__doc__:
readline.parse_and_bind("bind ^I rl_complete")
else: # GNU readline format
readline.parse_and_bind("tab: complete")

The documentation of the command syntax is in the .editrc man pages, for
example:

https://developer.apple.com/library/mac/#documentation/Darwin/Reference/M
anPages/man5/editrc.5.html

OK, change "no warranties" to "absolutely no warranties"

Good idea.