Python模塊「readline」無法處理輸出重定向

Question

我導入了readline，爲我的程序添加了自定義的選項卡完成。現在我需要保存程序的輸出，但是任何重定向stdout的嘗試都會破壞選項卡完成功能。

我試過python3 script.py | tee txt.txt女巫似乎最接近打印到標準輸出和文本文件，但它不起作用。

這裏是自定義選項卡完成類與函數調用主（以防萬一）：

import readline 

class MyCompleter(object): 

    def __init__(self, options): 
     self.options = sorted(options) 

    def complete(self, text, state): 
     if state == 0: 
      if text: 
       self.matches = [s for s in self.options if s and s.startswith(text)] 
      else: 
       self.matches = self.options[:] 
     try: 
      return self.matches[state] 
     except IndexError: 
      return None 

def readlineset(a): # function called from main to turn on tab completion 
        # a is list of strings 
    readline.set_completer(MyCompleter(a).complete) 
    readline.parse_and_bind('tab: complete') 

Answer 1

這裏是一個可能的解決方案：「猴子補丁」的sys.stdout.write方法，以便任何寫入stdout也得到發送到一個文件。我承認這不完全優雅，但它的工作原理。 ;）

我製作了Logger class a Context Manager，以便它可以在with語句中使用。

import readline 
import sys 

class MyCompleter(object): 
    def __init__(self, options): 
     self.options = sorted(options) 

    def complete(self, text, state): 
     if state == 0: 
      if text: 
       self.matches = [s for s in self.options if s and s.startswith(text)] 
      else: 
       self.matches = self.options[:] 
     try: 
      return self.matches[state] 
     except IndexError: 
      return None 

class Logger(object): 
    ''' Monkey-patch sys.stdout 
     to copy output to a file 
    ''' 
    def __init__(self, fname): 
     self.fh = open(fname, 'w') 
     self.oldwrite = sys.stdout.write 
     sys.stdout.write = self.write 

    def write(self, s): 
     self.oldwrite(s) 
     self.fh.write(s) 

    def close(self): 
     self.fh.close() 
     sys.stdout.write = self.oldwrite 

    # Define Context Manager methods so Logger 
    # can be used in a `with` statement 
    def __enter__(self): 
     return self 

    def __exit__(self, *args): 
     self.close() 
     return False 

def readlineset(a): 
    ''' Turn on tab completion. 
     `a` is list of strings that will be completed 
    ''' 
    readline.set_completer(MyCompleter(a).complete) 
    readline.parse_and_bind('tab: complete') 

def main(): 
    readlineset(['python', 'stack', 'overflow', 'exchange']) 
    with Logger('mylog.txt'): 
     while True: 
      s = input('> ') 
      if s == 'quit': 
       break 
      print(repr(s), len(s)) 

    print('bye') 

if __name__ == '__main__': 
    main() 

演示

> This is a test 
'This is a test' 14 
> python on stack overflow 
'python on stack overflow' 24 
> quit 
bye 

mylog.txt

'This is a test' 14 
'python on stack overflow' 24 

如果你不想使用with，您可以使用Logger這樣的：

def main(): 
    readlineset(['python', 'stack', 'overflow', 'exchange']) 
    logger = Logger('mylog.txt') 
    while True: 
     s = input('> ') 
     if s == 'quit': 
      break 
     print(repr(s), len(s)) 

    logger.close() 
    print('bye')