从 python 脚本运行外部交互式程序

Question

I have a python script which tries to execute external programs. My project involves a python talk bot through which the client should be able to execute commands in the remote terminal.

So basically the module incorporating the talk bot allows me only to get inputs and send output.I need to take the input and see if it is a terminal command and execute it.

So I used the subprocess.Popen object to implement this.

The problem is, if the command calls a program which is interactive, ie. waits for an input and gives output, I am not able to handle it. In the best case, Popen waits for all inputs and then gives the output.

Is there a way to do this properly, ie. start an external program and send input, get output; send input, get output and so on.

Answer 1

In my opinion the best model for this kind of problems is using an asynchronous single-threaded approach, but it requires code that is somewhat complex even with use of helping libraries.

Something conceptually simpler is the use of a multithread approach

import thread
import sys
import time

def repl():
    while True:
        print ">>> ",
        sys.stdout.flush()
        s = raw_input()
        exec s

def main_thread():
    for i in xrange(30):
        print i
        time.sleep(1)

thread.start_new_thread(repl, ())
main_thread()

In the above code the function repl waits for input and then execs whatever is entered at the prompt, but at the same time the main program is running (here it's not doing anything interesting, just counting up to 30).

Depending on how complex is your program this can be a reasonable solution. Note that after a certain level of parallel execution and logic complexity the multithread approach shows some drawback (complex and hard to debug locking logic)

Answer 2

pexpect may be what you need.