python——使用readline库实现tab自动补全

Input History

readline tracks the input history automatically. There are two different sets of functions for working with the history. The history for the current session can be accessed with get_current_history_length()and get_history_item(). That same history can be saved to a file to be reloaded later using write_history_file() and read_history_file(). By default the entire history is saved but the maximum length of the file can be set with set_history_length(). A length of -1 means no limit.

import readline
import logging
import os

LOG_FILENAME = '/tmp/completer.log'
HISTORY_FILENAME = '/tmp/completer.hist'

logging.basicConfig(filename=LOG_FILENAME,
                    level=logging.DEBUG,
                    )

def get_history_items():
    return [ readline.get_history_item(i)
             for i in xrange(1, readline.get_current_history_length() + 1)
             ]

class HistoryCompleter(object):

    def __init__(self):
        self.matches = []
        return

    def complete(self, text, state):
        response = None
        if state == 0:
            history_values = get_history_items()
            logging.debug('history: %s', history_values)
            if text:
                self.matches = sorted(h
                                      for h in history_values
                                      if h and h.startswith(text))
            else:
                self.matches = []
            logging.debug('matches: %s', self.matches)
        try:
            response = self.matches[state]
        except IndexError:
            response = None
        logging.debug('complete(%s, %s) => %s',
                      repr(text), state, repr(response))
        return response

def input_loop():
    if os.path.exists(HISTORY_FILENAME):
        readline.read_history_file(HISTORY_FILENAME)
    print 'Max history file length:', readline.get_history_length()
    print 'Startup history:', get_history_items()
    try:
        while True:
            line = raw_input('Prompt ("stop" to quit): ')
            if line == 'stop':
                break
            if line:
                print 'Adding "%s" to the history' % line
    finally:
        print 'Final history:', get_history_items()
        readline.write_history_file(HISTORY_FILENAME)

# Register our completer function
readline.set_completer(HistoryCompleter().complete)

# Use the tab key for completion
readline.parse_and_bind('tab: complete')

# Prompt the user for text
input_loop()

The HistoryCompleter remembers everything you type and uses those values when completing subsequent inputs.

$ python readline_history.py
Max history file length: -1
Startup history: []
Prompt ("stop" to quit): foo
Adding "foo" to the history
Prompt ("stop" to quit): bar
Adding "bar" to the history
Prompt ("stop" to quit): blah
Adding "blah" to the history
Prompt ("stop" to quit): b
bar   blah
Prompt ("stop" to quit): b
Prompt ("stop" to quit): stop
Final history: ['foo', 'bar', 'blah', 'stop']

The log shows this output when the “b” is followed by two TABs.

DEBUG:root:history: ['foo', 'bar', 'blah']
DEBUG:root:matches: ['bar', 'blah']
DEBUG:root:complete('b', 0) => 'bar'
DEBUG:root:complete('b', 1) => 'blah'
DEBUG:root:complete('b', 2) => None
DEBUG:root:history: ['foo', 'bar', 'blah']
DEBUG:root:matches: ['bar', 'blah']
DEBUG:root:complete('b', 0) => 'bar'
DEBUG:root:complete('b', 1) => 'blah'
DEBUG:root:complete('b', 2) => None

When the script is run the second time, all of the history is read from the file.

$ python readline_history.py
Max history file length: -1
Startup history: ['foo', 'bar', 'blah', 'stop']
Prompt ("stop" to quit):

There are functions for removing individual history items and clearing the entire history, as well.

最后效果是你输入的历史的foo被记录了下来，下次打开的时候输入fo然后tab就可以自动提示foo来补全了！