python - 与Python子进程通信

Question

我有以下Rust代码，它通过stdin将字符串发送到子进程，并读取来自stdout的所有内容:

use std::io::{BufRead, BufReader, Write};
use std::process::{Command, Stdio};
fn main() {
   let mut child = Command::new("cat")
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .spawn()
        .expect("Did not run");
    let v = vec!["11111", "2222222", "3333", "end", "soooooooooooooooo"];
    let k = child.stdin.as_mut().unwrap();
    let mut g = BufReader::new(child.stdout.as_mut().unwrap());
    for x in v.into_iter() {
        k.write_all(x.as_bytes()).unwrap();
        k.write_all("\n".as_bytes()).unwrap();
        let mut s: String = String::new();
        g.read_line(&mut s).unwrap();
        println!("{}", s)
    }
}

该示例运行时没有问题，但是当我尝试使用python脚本执行相同操作时，它失败了。

要调用脚本，我正在创建child，如下所示:

    let mut child = Command::new("c:\\Windows\\py.exe")
        .args(&["-u", "echo.py"])

在脚本中，我只是回显从stdin到stdout的任何内容

import sys
import time
if __name__=="__main__":
    fo=sys.stdout
    fo.write('python starts at: %.0f\n'%(time.time()*1000))
    line = sys.stdin.readline()
    while True:
        fo.write(line+"\n")
        line = sys.stdin.readline()
    fo.write('python ends at: %.0f\n'%(time.time()*1000))

我得到的输出是:

python starts at: 1582166542281                                                                

11111                                                                                          



2222222                                                                                        



Traceback (most recent call last):                                                             
  File "c:\Users\asia\Documents\projects\python\echo.py", line 8, in <module>                  
    fo.write(line+"\n")                                                                        
OSError: [Errno 22] Invalid argument                                                           

我的想法是在打印第二个字符串周围的管道中断，但是我不知道为什么。我在这里想念什么？

提前致谢

Answer 1

Rust进程在python进程的stdin上写了5行，精确地来自以下字符串:

let v = vec!["11111", "2222222", "3333", "end", "soooooooooooooooo"];

但是在python方面，您尝试写回 rust 7行: header ，接下来的5行
来自stdin和页脚。
read_line中的for x in v.into_iter()仅读取5行并且rust进程终止，从而在python端触发了BrokenPipe，而该行又不得不再写两行。

我认为还需要一些控制来退出python端的while True循环。

遵循这些思路，只是为了了解一下:

use std::io::{BufRead, BufReader, Write};
use std::process::{Command, Stdio};
fn main() {
   let mut child = Command::new("python").args(&["-u", "echo.py"])
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .spawn()
        .expect("Did not run");
    let v = vec!["11111", "2222222", "3333", "end", "soooooooooooooooo"];
    let k = child.stdin.as_mut().unwrap();
    let mut g = BufReader::new(child.stdout.as_mut().unwrap());

    // read the header "python starts at ..."
    let mut s: String = String::new();
    g.read_line(&mut s).unwrap();
    println!("{}", s);

    for x in v.into_iter() {
        k.write_all(x.as_bytes()).unwrap();
        k.write_all("\n".as_bytes()).unwrap();
        let mut s: String = String::new();

        // read len(v) lines, in this case 5 lines
        g.read_line(&mut s).unwrap();
        println!("{}", s)
    }

    // Something is neeeded to signal termination of input
    // assume for this example a zero length string
    k.write_all("\n".as_bytes()).unwrap();

    // read the empty string and the footer "python ends at ..."
    let mut s: String = String::new();
    g.read_line(&mut s).unwrap();
    g.read_line(&mut s).unwrap();
    println!("{}", s);
}

Python:

import sys
import time

if __name__ == "__main__":
    fo = sys.stdout
    fo.write('python starts at: %.0f\n' % (time.time()*1000))
    line = sys.stdin.readline()
    while True:
        fo.write(line)
        line = sys.stdin.readline()
        if (line == "\n"):
            break

    fo.write('python ends at: %.0f\n' % (time.time()*1000))