How to use gnu readline library in program?

[Peter Otten]

Grant Edwards wrote:

> I'm trying to figure out how to use the gnu readline library so
> that when my program is prompting the user for input there is
> line editing and history support.
> 
> I've read and re-read the documentation for the "readline"
> module in the standard library and I still can't figure out how
> to use the module or even if the module is intended to do what
> I want.  The example code all seems to be about on how to
> modify the behavior of an interactive Python interpreter
> session so you have things like auto-completion of Python
> identifiers.
> 
> What I want to do is replace sys.stdin.readline() with
> something that will provide the user with line editing and
> history recall.  In other languages, one uses the Gnu readline
> library to do that, but my reading of the Python library
> documentation is that's not what the Python readline module is
> for. Am I wrong?

Here's a simple example:
 
import readline

for s in "alpha beta gamma".split():
    readline.add_history(s)

candidates = "red yellow pink blue black".split()

def completer(word, index):
    matches = [c for c in candidates if c.startswith(word)]
    try:
        return matches[index] + " "
    except IndexError:
        pass


readline.set_completer(completer)
readline.parse_and_bind("tab: complete")

while 1:
    print raw_input("$ ")

You may also consider using the cmd module.

Peter