使用子进程捕获输入和输出（运行 java 的 Python）

Question

I'm wanting to write testing scripts for Java classes using Python. I am able to compile, run, provide input, and capture output using subprocess , java.util.Scanner , and other tools. The code runs, but I'm not capturing the run log I was hoping to.

The Issue

As of now the output is captured without including the input... I'm getting (where 1, 2, 3, 4 is the input from a file):

Number? Number? Number? Number? Sum: 10

I want to capture:

Number? 1
Number? 2
Number? 3
Number? 4
Sum: 10

Current Code
Python

import os.path, subprocess

def compile_java(java_file, inputFile):
    #setup input file
    stdin = get_expected(inputFile)

    #compile java
    subprocess.check_call(['javac', java_file])

    #prep for running
    java_class, ext = os.path.splitext(java_file)
    cmd = ['java', java_class]

    #run java with input, and capturing output
    proc = subprocess.run(cmd, input=stdin, check=True, capture_output=True, text=True)

    print(proc.stdout)

def get_expected(filename):
    content = ""
    with open(f'{filename}', 'r') as f:
        for line in f.readlines():
            content += line
    return content

compile_java('Example.java', 'example.in')

Java - Example.java

import java.util.*;

public class Example{
      public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        
        int sum = 0;
        for(int i =0; i < 4; i++){
           System.out.print("Number? ");
           sum = sum + scan.nextInt();
        }
        System.out.println("Sum: " + sum);
     }
}

Input File - example.in

1
2
3
4

Note: I'm wanting to test the Java file, so I don't want to edit the Java in any way. I'm hoping there is a way I can capture the output in this format through just changing the Python code.

Answer 1

If you just want to capture your output in that format, why not do the following:

for(int i =0; i < 4; i++){
    int a = scan.nextInt();
    System.out.println("Number? " + a);
    sum = sum + a;
}