Python pexpect 模块交互方法过滤器

Question

我是Python新手，我正在尝试使用pexpect，对interact的输入/输出过滤器感兴趣。但我不知道如何使用过滤器。

在Pexpect的文档中，关于交互方法，提到:

interact(escape_character=’x1d’, input_filter=None, output_filter=None)

This gives control of the child process to the interactive user (the human at 
the keyboard). Keystrokes are sent to the child process, and the stdout and stderr 
output of the child process  is printed. This simply echos the child stdout and child 
stderr to the real stdout and it echos the real stdin to the child stdin. When the 
user types the escape_character this method  will stop. The default for 
escape_character is ^]. This should not be confused with ASCII 27 –  the ESC 
character. ASCII 29 was 
chosen for historical merit because this is the character used by ‘telnet’ as the 
escape character. The escape_character will not be sent to the child process.

You may pass in optional input and output filter functions. These functions should 
take a string and return a string. The output_filter will be passed all the output 
from the child process. The input_filter will be passed all the keyboard input from 
the user. The input_filter is run BEFORE the check for the escape_character.

但是没有任何示例如何使用输入或输出过滤器。唯一的就是它提到的是，“这些函数应该接受一个字符串并返回一个字符串”。

例如，如果我想在每个用户输入中附加“aaa”，我该怎么做？ (过滤器应该是什么？)

def my_input(str):
    return str + "aaa"
...
...
c.interact(input_filter=?)

提前致谢。

Answer 1

当 pexpect 从底层文件描述符中读取输入/输出的每个 block 时，它会被传递。这可能是从单个字节到 1000 个字节的任何位置，具体取决于发生的情况。

如果您想在每行末尾添加一些内容，您需要编写一个检查换行符的函数。像这样的东西(未经测试):

def filter(input):
    return input.replace(b'\r\n', b'aaa\r\n')

c.interact(input_filter=filter)