How to use gnu readline library in program?

[Grant Edwards]

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?

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[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

[Grant Edwards]

>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("$ ")

Ah, thanks. It was far too simple. What I was looking for was
simply:

import readline

then replace sys.stdin.readline() with raw_input()

You may also consider using the cmd module.

I'll have to keep the cmd module in mind for other applications
(where the user is entering commands). Rather than commands,
the user of this application is entering data that changes
little (if any) from one line to the next, so raw_input() is
exactly what I needed.

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