How to write code to autocomplete words and sentences?

Question

I'd like to write code that does autocompletion in the Linux terminal. The code should work as follows.

It has a list of strings (e.g. "hello, "hi", "how are you", "goodbye", "great", ...).

In the terminal, the user will start typing and when there is some match possibility, he gets the hint for possible strings, from which he can choose (similarly as in vim editor or google incremental search).

e.g. he starts typing "h", and he gets the hint

h"ello"

_ "i"

_"ow are you"

And better yet would be if it would complete words not only from the beginning, but from an arbitrary part of the string.

Answer 1

(I'm aware this isn't exactly what you're asking for, but) If you're happy with the auto-completion/suggestions appearing on TAB (as used in many shells), then you can quickly get up and running using the readline module.

Here's a quick example based on Doug Hellmann's PyMOTW writeup on readline.

import readline  class MyCompleter(object):  # Custom completer      def __init__(self, options):         self.options = sorted(options)      def complete(self, text, state):         if state == 0:  # on first trigger, build possible matches             if text:  # cache matches (entries that start with entered text)                 self.matches = [s for s in self.options                                      if s and s.startswith(text)]             else:  # no text entered, all matches possible                 self.matches = self.options[:]          # return match indexed by state         try:              return self.matches[state]         except IndexError:             return None  completer = MyCompleter(["hello", "hi", "how are you", "goodbye", "great"]) readline.set_completer(completer.complete) readline.parse_and_bind('tab: complete')  input = raw_input("Input: ") print "You entered", input 

This results in the following behaviour (<TAB> representing a the tab key being pressed):

Input: <TAB><TAB> goodbye      great        hello        hi           how are you  Input: h<TAB><TAB> hello        hi           how are you  Input: ho<TAB>ow are you 

In the last line (HOTAB entered), there is only one possible match and the whole sentence "how are you" is auto completed.

Check out the linked articles for more information on readline.

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"And better yet would be if it would complete words not only from the beginning ... completion from arbitrary part of the string."

This can be achieved by simply modifying the match criteria in the completer function, ie. from:

self.matches = [s for s in self.options                     if s and s.startswith(text)] 

to something like:

self.matches = [s for s in self.options                     if text in s] 

This will give you the following behaviour:

Input: <TAB><TAB> goodbye      great        hello        hi           how are you  Input: o<TAB><TAB> goodbye      hello        how are you 

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Updates: using the history buffer (as mentioned in comments)

A simple way to create a pseudo-menu for scrolling/searching is to load the keywords into the history buffer. You will then be able to scroll through the entries using the up/down arrow keys as well as use Ctrl+R to perform a reverse-search.

To try this out, make the following changes:

keywords = ["hello", "hi", "how are you", "goodbye", "great"] completer = MyCompleter(keywords) readline.set_completer(completer.complete) readline.parse_and_bind('tab: complete') for kw in keywords:     readline.add_history(kw)  input = raw_input("Input: ") print "You entered", input 

When you run the script, try typing Ctrl+r followed by a. That will return the first match that contains "a". Enter Ctrl+r again for the next match. To select an entry, press ENTER.

Also try using the UP/DOWN keys to scroll through the keywords.

Answer 2

To enable autocomplete in a Python shell, type this:

import rlcompleter, readline readline.parse_and_bind('tab:complete') 

(thanks to http://blog.e-shell.org/221)