第十四章：应用构建模块-readline: GNU readline库-输入历史

14.3.4 输入历史
readline会自动跟踪输入历史。有两组不同的函数来处理历史。当前会话的历史可以使用get_current_history_length()和get_history_item()访问。这个历史可以保存到一个文件中，以后分别用write_history_file()和read_history_file()重新加载。默认地会保存整个历史，不过可以用set_history_length()设置文件的最大长度。如果值为-1，则表示长度没有限制。

try:
    import gnureadline as readline
except ImportError:
    import readline
import logging
import os

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

logging.basicConfig(
    format='%(message)s',
    filename=LOG_FILENAME,
    level=logging.DEBUG,
    )

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

class HistoryCompleter:

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


    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 = input('Prompt ("stop" to quit): ')
            if line == 'stop':
                break
            if line:
                print('Adding {!r} to the history'.format(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()

HistoryCompleter记住键入的所有内容，并在完成后续输入时使用这些值。

按下b后再按下两次tab，日志会显示以下输出。

第二次运行脚本时，将从文件读取所有历史。

还有一些函数可以删除单个历史项，也可以清除整个历史。