[Patches] [ python-Patches-494066 ] Access to readline history elements

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Patches item #494066, was opened at 2001-12-16 20:04
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Category: Library (Lib)
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Chuck Blake (cblake)
Assigned to: Nobody/Anonymous (nobody)
Summary: Access to readline history elements

Initial Comment:
The current readlinemodule.c has a relatively minimal
wrapper around the functionality of the GNU readline
and history libraries.  That may be fine, and since
some try to use libeditline instead it may be the best.

However the current module does not enable any access
from within Python to the libreadline maintained list
of input lines.  The ideal thing would be to actually
export that dynamically maintained C list as a Python 
object.  In lieu of that more complex change, my patch
simply adds very simple history_get() and history_len()
methods.  This is the least one needs to access the
list.  I'm pretty sure the library functions go waaaay
back, probably to the merger of the history and
readline libraries.

This patch also adds one final little ingredient which
is rl_redisplay() in the wrapper for rl_insert_text().
Without this the user cannot see the inserted text
until they type another character, which seems pretty
undesirable.

Together these two updates allow the regular Unix
readline-enabled shell to perform "auto indentation".
I.e., inserting into the edit buffer the leading 
whitespace from the preceding non-result producing
line.  Since it can be editted, one can just backspace
a couple times to reverse the autoindent.

This makes the basic readline-enabled read-eval-print 
loop substantially more pleasant.  I can provide an
example PYTHONSTARTUP file that shows how to use it.
Only a tiny 8 line or so pre_input_hook is needed and
a slightly smart sys.ps1 or sys.ps2 object that
communicates via a variable to our hook function 
whether or not the parser is expecting more input.

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>Comment By: Guido van Rossum (gvanrossum)
Date: 2001-12-17 11:40

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Hm, I was going to see if the insert_text fix was a simple
enough fix to apply to 2.2, but I don't have an example of
where this is needed. If I call it from the startup hook the
text I insert is already being displayed.

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