如何運行2個行程并在它們之間多次交換輸入/輸出？

我正在嘗試做這樣的事情：

Future<String> getOutAndAnswer(testcase) async {
  Process python = await Process.start('python', ['tasks/histogram/run.py']);

  Process java = await Process.start('java', ['solutions/Histogram.java']);

  String results = "";

  for(int i = 0; i < testcase; i  ){
    final String out = await python.stdout.transform(utf8.decoder).first;

    java.stdin.writeln(out);

    final String answer = await java.stdout.transform(utf8.decoder).first;

    python.stdin.writeln(answer);

    results  = "($out, $answer)";
  }

  return results;
}

基本上，python 程式負責生成每個測驗用例的輸入，然后 java 程式將獲取輸入并回傳答案，然后將其發送給 python 程式以檢查它是否正確，等等。案子。

但是當我嘗試使用上面的代碼時，我得到一個錯誤，說我已經聽過一次流了：

Exception has occurred.
StateError (Bad state: Stream has already been listened to.)

蟒蛇程式：

import os

CASE_DIR = os.path.join(os.path.dirname(__file__), "cases")

test_cases = next(os.walk(CASE_DIR))[2]

print(len(test_cases))
for case in sorted(test_cases):
    with open(os.path.join(CASE_DIR, case), 'r') as f:
        print(f.readline(), end='', flush=True)
        f.readline()
        
        expected_output = f.readline()

        user_output = input()
        
        if expected_output != user_output:
            raise ValueError("Wrong answer!")

print("EXIT", flush=True)

Java程式：

public class Histogram {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int t = scanner.nextInt();
        for (int i = 0; i < t; i  ) {
            String input = scanner.nextLine();

            String answer = calculateAnswer(input);

            System.out.println(answer);
        }
    }
}

uj5u.com熱心網友回復：

您的問題是.first哪個要監聽流，獲取第一個元素，然后立即停止監聽流。請參閱此處的檔案：https ://api.dart.dev/stable/2.17.3/dart-async/Stream/first.html

相反，您應該聽一次并定義一種onData方法來執行這些步驟。請參閱.listen()此處的檔案：https ://api.dart.dev/stable/2.17.3/dart-async/Stream/listen.html

uj5u.com熱心網友回復：

您可以嘗試將標準輸出流包裝在StreamIterator<String>. 您將不得不嘗試驗證，但我認為這就是您正在尋找的。

Future<String> getOutAndAnswer(int testcase) async {
  Process python = await Process.start('python', ['tasks/histogram/run.py']);
  Process java = await Process.start('java', ['solutions/Histogram.java']);

  String results = "";

  StreamIterator<String> pythonIterator = StreamIterator(
      python.stdout.transform(utf8.decoder).transform(LineSplitter()));
  StreamIterator<String> javaIterator = StreamIterator(
      java.stdout.transform(utf8.decoder).transform(LineSplitter()));

  for (int i = 0; i < testcase; i  ) {
    if (await pythonIterator.moveNext()) {
      final String out = pythonIterator.current;
      if (out == 'EXIT') {
        break;
      }

      java.stdin.writeln(out);

      if (await javaIterator.moveNext()) {
        final String answer = javaIterator.current;

        python.stdin.writeln(answer);

        results  = "($out, $answer)";
      }
    }
  }

  await pythonIterator.cancel();
  await javaIterator.cancel();
  return results;
}

您可能需要添加以下匯入：

import 'dart:async';
import 'dart:convert';

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